Add support for showing code flows

[charisk]

Adds the ability to read code flow information from SARIF files and render those in the Web View.

A few notes:

• I've used an RC version of the Primer React library to take advantage of some of the new menu/overlay stuff. I don't intend to merge the PR until the final version is released (see Primer React v35 RC - Technical Preview primer/react#1918).
• As discussed previously, we need a better solution for the validation aspect of SARIF data.

Checklist

N/A:

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[aeisenberg]

Looks good. My main comment about trying your best to display malformed source locs can be delayed until later.

[charisk]

There is a bit of a delay with releasing a new version of Primer React so I'll go ahead and merge this PR since none of the RC issues seem to be affecting us. I'll come back and upgrade the package versions once a new version is released.