CodeQL docs: update titles, add intros, and a few content updates (CodeQL for C/C++)

[jf205]

The PR makes a start at addressing the tasks in https://github.com/github/product-documentation/issues/2163.

tldr for any members of the C analysis team who stumble upon this: We are trying to align the CodeQL documentation with the style and structure used in the GitHub help docs. There will be a series of PRs with updates. We'll try not to do anything that could change the technical meaning of the text and may ping you with questions as we are going along.

Summary of changes

• Update titles
• Update links to account for new titles
• Add intros
• Rework the CodeQL for C and C++ homepage to include only the autogenerated TOC.
• Some small changes to content:
  • Attempt to make the flow from the new intro to the main article a bit smoother
  • Fix a few inline links

TODO

Possibly next PR:

• Rework further reading sections, and save in a reusable snippet as suggested by @felicitymay in CodeQL: Python topics (2166) - WIP #2823. I'll wait until that PR is merged to avoid conflicts.
• More thorough review for localization issues.

Later PRs:

• Think long and hard about the most appropriate content models to apply.
• Review content, adding referential, conceptual, and procedural sections in certain topics.

For more info, see notes on https://github.com/github/product-documentation/issues/2163.

[felicitymay]

These changes all look good. I wonder if a couple of the introductions really add much to the title, but haven't commented because the PRs we've opened so far all view this differently. This is something that it would be good to discuss as a group - topics like the library introductions should probably have fairly similar introductions.

[felicitymay]

Not required for this PR, but this note should probably have been deleted or clarified when we moved the documentation out of LGTM. We should probably check other languages for similar notes.

[shati-patel]

This looks good overall! (I've just made some suggestions to use the exact title when linking.)

I agree that we need to decide on more consistent intros (and possibly titles) across the languages. @felicitymay is making notes on these kind of tasks, so we can discuss that as a group later.

[jf205]

@shati-patel, @felicitymay: thanks for the comments and suggestions. Is there anything else you think I should address now? (I intend to revisit this when all of the other initial 'CodeQL for X' PRs have been completed, as mentioned on #2866 and #2823.)

[felicitymay]

Thanks for the updates 👍

[jf205]

I removed the WIP label now. Any further thoughts before i merge?

[felicitymay]

I think this is fine to merge as-is.