Fix buffer copying for HybridCachePayload.

[cincuranet]

Fixes #7342.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR fixes a critical bug in HybridCache's payload parsing logic that caused an ArgumentException when retrieving cached entries with multiple tags. The issue occurred when parsing cached data with 2+ tags while passing empty knownTags, causing all tags to be moved into a pending tags buffer. The code incorrectly used Array.CopyTo() to copy from an oversized ArrayPool-rented buffer to an exact-sized destination array, attempting to copy more elements than the destination could hold.

Changes:

• Fixed buffer copying in HybridCachePayload.TryParse to use Array.Copy with explicit count instead of CopyTo
• Added comprehensive test coverage for the scenario with 2 and 3 pending tags

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Libraries/Microsoft.Extensions.Caching.Hybrid/Internal/HybridCachePayload.cs	Changed line 312 from pendingTagBuffer.CopyTo(final, 0) to Array.Copy(pendingTagBuffer, final, pendingTagsCount) to copy only the used portion of the rented buffer
test/Libraries/Microsoft.Extensions.Caching.Hybrid.Tests/PayloadTests.cs	Added RoundTrip_WithPendingTags_WhenKnownTagsMismatch theory test with 2 and 3 tag scenarios to verify the fix

[rosebyte]

LGTM