Update version and fix version increment scripts

[weshaggard]

• Increments version after last release.
• Fixes Update-Version script to work with the new repo structure
• Update changelog parsing code to preserve existing header blocks (I will port this to azure-sdk-tools eng/common as well).

[Copilot]

Pull Request Overview

This PR increments the version to 0.5.9 and fixes the version increment scripts to work with the new repository structure. The changes also improve changelog parsing to preserve existing header blocks for better integration with azure-sdk-tools.

• Increments version from 0.5.8 to 0.5.9 in project file
• Adds new changelog entry template for version 0.5.9
• Fixes parameter ordering in Update-Version.ps1 script
• Enhances changelog parsing to preserve custom header blocks

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
Azure.Mcp.Server.csproj	Updates version number from 0.5.8 to 0.5.9
CHANGELOG.md	Adds new unreleased version 0.5.9 entry template
Update-Version.ps1	Fixes parameter ordering by moving ServerName parameter
ChangeLog-Operations.ps1	Adds header block preservation functionality