Add changelog render --no-descriptions

[lcawl]

This PR enhances the "changelog render" command with a --no-descriptions option similar to what was accomplished in changelog directives via #3224
In this case, however, we've omitted the auto behavior to keep it simple.

NOTE: This PR also incorporates #3272, since I figured it was dependent on this one.

Screenshots

Before

In #3262, asciidoc output:

• Descriptions in breaking changes and deprecations:
  

• Descriptions in fixes and enhancements:
  

After

Asciidoc output:

• Descriptions omitted from breaking changes and descriptions:
  

• Descriptions omitted from fixes and enhancements:
  

AI summary

The implementation works with both --file-type markdown and --file-type asciidoc, hiding entry descriptions while preserving all other content (titles, links, Impact/Action sections, bundle descriptions).

1. CLI Parameter & Arguments

• Added bool noDescriptions = false parameter to ChangelogCommand.Render
• Added HideDescriptions property to RenderChangelogsArguments
• Updated parameter documentation

2. Render Context

• Added HideDescriptions property to ChangelogRenderContext
• Updated BuildRenderContext to pass through the flag

3. All Renderers Updated

Markdown Renderers (--file-type markdown):

• ✅ IndexMarkdownRenderer - gates description in bulleted lists
• ✅ BreakingChangesMarkdownRenderer - gates description in both dropdown and flattened modes
• ✅ DeprecationsMarkdownRenderer - gates description in both modes
• ✅ KnownIssuesMarkdownRenderer - gates description in both modes
• ✅ HighlightsMarkdownRenderer - gates description in both modes

AsciiDoc Renderers (--file-type asciidoc):

• ✅ AsciidocRendererBase.RenderEntryDescription() - updated to return early when context.HideDescriptions is true
• This automatically affects all concrete AsciiDoc renderers

4. Comprehensive Tests

• ✅ Created tests/Elastic.Changelog.Tests/Changelogs/Render/DescriptionVisibilityTests.cs
• Tests cover both markdown and asciidoc formats
• Tests verify descriptions are hidden while preserving titles, links, Impact/Action
• Tests cover both dropdown and flattened modes
• Tests verify bundle descriptions remain visible

5. Documentation

• ✅ Updated docs/cli/changelog/render.md with --no-descriptions flag documentation

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

2. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used: composer-2, claude-4-sonnet-thinking