Add ConfigurableCredential test coverage for all credential types

[m-nash]

Resolves #55501

What this PR does

Adds comprehensive test coverage for creating Azure Identity credentials via IConfiguration and the internal ConfigurableCredential class, ensuring both direct instantiation and configuration-based creation paths produce identical behavior.

Changes

Source (2 files):

• DefaultAzureCredentialOptions.cs — Added internal \IsAzureProxyEnabled\ property with IConfig reading and Clone support
• DefaultAzureCredentialFactory.cs — Copies \IsAzureProxyEnabled\ to WIC options

Test infrastructure (3 files modified):

• \WorkloadIdentityCredentialTests.cs\ — Added virtual factory methods for credential creation
• \CredentialTestHelpers.cs\ — \GetMsalClientType\ unwraps \ConfigurableCredential\
• \ConfigurableCredentialTestHelper.cs\ — Castle proxy unwrap, public config mapping, transport support

New test files (9 files):

• \CredentialCreationTestBase\ — Shared base with \ReadProperty/\ReadField\ reflection helpers
• Configurable \WorkloadIdentityCredentialTests\ — Credential creation via IConfiguration (54 pass, 2 skipped — matches base class)
• 7 creation test classes validating option priority (IConfig > env var > default):

  Credential	Tests	Properties Covered
  WorkloadIdentity	19	TenantId, ClientId, TokenFilePath, AuthorityHost, DisableInstanceDiscovery, IsUnsafeSupportLoggingEnabled, AdditionallyAllowedTenants, IsAzureProxyEnabled
  AzureCli	15	TenantId, Subscription, ProcessTimeout, AdditionallyAllowedTenants, IsUnsafeSupportLoggingEnabled
  AzurePowerShell	12	TenantId, ProcessTimeout, AdditionallyAllowedTenants, IsUnsafeSupportLoggingEnabled
  AzureDeveloperCli	12	TenantId, ProcessTimeout, AdditionallyAllowedTenants, IsUnsafeSupportLoggingEnabled
  VisualStudio	12	TenantId, ProcessTimeout, AdditionallyAllowedTenants, IsUnsafeSupportLoggingEnabled
  VisualStudioCode	12	TenantId, AdditionallyAllowedTenants, AuthorityHost, IsUnsafeSupportLoggingEnabled
  Environment	15	TenantId, ClientId, AuthorityHost, DisableInstanceDiscovery, IsUnsafeSupportLoggingEnabled, AdditionallyAllowedTenants

Total: 92 creation tests + 56 configurable WIC tests, all passing

[Copilot]

Pull request overview

This PR expands Azure.Identity’s test suite to validate that all supported credential types can be created via IConfiguration (through the internal ConfigurableCredential path) with the same effective option behavior as direct instantiation—especially around option precedence (config > env vars > defaults) and Workload Identity’s Azure proxy opt-in.

Changes:

• Added internal IsAzureProxyEnabled plumbing from IConfiguration into DefaultAzureCredentialOptions, with clone support and factory propagation into WorkloadIdentityCredentialOptions.
• Refactored the existing WorkloadIdentityCredentialTests to introduce overridable factory methods, enabling a configurable-test variant to reuse the same base assertions.
• Introduced a shared CredentialCreationTestBase<T> plus multiple new “creation/priority” test classes under tests/ConfigurableCredentials/ to validate configuration mapping and precedence for each credential type.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
sdk/identity/Azure.Identity/src/Credentials/DefaultAzureCredentialOptions.cs	Reads IsAzureProxyEnabled from config and preserves it during cloning for config-based credential creation.
sdk/identity/Azure.Identity/src/DefaultAzureCredentialFactory.cs	Propagates IsAzureProxyEnabled into WorkloadIdentityCredentialOptions when creating a WIC via DAC/config path.
sdk/identity/Azure.Identity/tests/WorkloadIdentityCredentialTests.cs	Adds virtual factory methods and exposes temp-file helper to enable reuse by configurable credential tests.
sdk/identity/Azure.Identity/tests/CredentialTestHelpers.cs	Updates MSAL-client-type detection to unwrap ConfigurableCredential so shared MSAL-oriented base tests work with configurable credentials.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/ConfigurableCredentialTestHelper.cs	Adds Castle proxy unwrapping and transport injection support for configurable credential tests.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/CredentialCreationTestBase.cs	New shared base for config-driven credential creation + reflection helpers used by option-precedence tests.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/WorkloadIdentityCredentialTests.cs	New configurable variant of the WIC test suite that creates credentials via IConfiguration.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/WorkloadIdentityCredentialCreationTests.cs	New option precedence and mapping tests for WorkloadIdentityCredentialOptions (including Azure proxy behavior).
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/AzureCliCredentialCreationTests.cs	New option precedence tests for Azure CLI credential creation via config.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/AzurePowerShellCredentialCreationTests.cs	New option precedence tests for Azure PowerShell credential creation via config.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/AzureDeveloperCliCredentialCreationTests.cs	New option precedence tests for Azure Developer CLI credential creation via config.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/VisualStudioCredentialCreationTests.cs	New option precedence tests for Visual Studio credential creation via config.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/VisualStudioCodeCredentialCreationTests.cs	New option precedence tests for Visual Studio Code credential creation via config.
sdk/identity/Azure.Identity/tests/ConfigurableCredentials/EnvironmentCredentialCreationTests.cs	New option precedence tests for Environment credential creation via config (authority host, tenants, etc.).

[m-nash]

/check-enforcer override