Add Parse-ChangelogContent and Set-ChangeLogEntryContent to common scripts

[Copilot]

Promotes changelog parsing logic from Java SDK's Changelog-Helpers.ps1 to shared common scripts per discussion in Azure/azure-sdk-for-java#47079.

Changes

• Parse-ChangelogContent: Parses raw changelog text into structured ReleaseContent array and Sections hashtable
• Set-ChangeLogEntryContent: Updates a changelog entry with parsed content from new text
• Get-SectionHeaderRegex: Shared helper function for building section header regex patterns, used by Get-ChangeLogEntriesFromContent, Parse-ChangelogContent, and Remove-EmptySections
• Pester tests: 12 tests covering unit and integration scenarios

Local run the pester tests, all passed:

Usage

$entries = Get-ChangeLogEntries -ChangeLogLocation "CHANGELOG.md"
$entry = $entries["1.0.0"]

# Update entry with generated changelog text
Set-ChangeLogEntryContent -ChangeLogEntry $entry `
    -NewContent "### Features Added`n`n- New feature" `
    -InitialAtxHeader $entries.InitialAtxHeader

Set-ChangeLogContent -ChangeLogLocation "CHANGELOG.md" -ChangeLogEntries $entries

These functions enable SDK automation tools to programmatically update changelogs with generated content while maintaining proper structure.

• Fixes Changelog operations, promote common logics from Java's implemeted scripts to Engsys common scripts #13044

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[haolingdong-msft]

Local run the pester tests, all passed:

[Copilot]

Pull request overview

This PR promotes changelog parsing logic from the Java SDK to shared common scripts, introducing two new functions to programmatically update changelog entries while maintaining structure.

Purpose: Enable SDK automation tools across different language repositories to programmatically update changelogs with generated content.

Key Changes:

• Added New-ChangelogContent function to parse raw changelog text into structured content (ReleaseContent array and Sections hashtable)
• Added Set-ChangeLogEntryContent function to update changelog entries with new parsed content
• Comprehensive Pester test suite with 12 tests covering unit and integration scenarios

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
eng/common/scripts/ChangeLog-Operations.ps1	Adds two new helper functions (New-ChangelogContent and Set-ChangeLogEntryContent) for parsing and updating changelog entries programmatically
eng/common-tests/ChangeLog-Operations.Tests.ps1	Introduces comprehensive Pester tests (12 tests total) covering unit tests for both new functions and integration tests for the complete update workflow

[weshaggard]

/azp run azure-sdk-tools - sync - eng-common

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[azure-sdk]

The following pipelines have been queued for testing:
java - template
java - template - tests
js - template
net - template
net - template - tests
python - template
python - template - tests
You can sign off on the approval gate to test the release stage of each pipeline.
See eng/common workflow