[various] Add unintended_html_in_doc_comment to analysis options

[stuartmorgan-g]

Adds unintended_html_in_doc_comment to our analysis options, and fixes violations.

This does a version bump even for cases where the comments being fixed are internal, because part of the goal here is to eliminate pana deductions on pub.dev, and that doesn't take into account whether the violation is client-facing or just package-developer-facing.

Fixes flutter/flutter#183860

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩²

[stuartmorgan-g]

This was just opportunistic cleanup to a test file I was already editing, since I happened to notice it. We already require package:web 1.0+ for example.

[gemini-code-assist]

Code Review

This pull request introduces the unintended_html_in_doc_comment lint rule to the analysis options and addresses violations across several packages. The changes primarily involve replacing HTML-like tags in Dart doc comments with markdown code blocks (e.g., changing <T> to <T> or adding ```dart blocks for code examples). This is a valuable improvement for documentation clarity and consistency, aligning with best practices for Dartdoc. Version numbers in pubspec.yaml and `CHANGELOG.md` files have been updated accordingly for the affected packages.