Bring Code Quality inline diff display closer to inline findings designs

🆕 See epic &8071 (closed) for implementation issues

Scope of issue

Design │ MVC │ Inline findings in the MR (#322689 - closed) outlines a future direction for security analyzer and Code Quality findings in diffs.

The goal of the issue is to:

• identify gaps between the current Code Quality implementation and the designs in that issue.
• create issues (or directly create MRs) to bring the feature closer to the future design.

Hopefully this serves at least two goals:

• We make the existing feature better for users.
• We become familiar with the existing feature implementation and can more readily adapt it in the future.

The existing feature diverges from the new designs in at least a couple of ways:

• The severity indicator is placed differently (see #322689[design_1639471104105.png])
• The severity indicator should handle >1 finding per line (see #322689[design_1643146383226.png]); I believe it can only handle one today
• The findings are shown in a tooltip, rather than the presentation in #322689[design_1643147487036.png]

Here's an example CQ diff for convenience: jheimbuck_gl/code_quality_example!21 (diffs)

There are definitely things that will be out of scope until we can bring SAST, Secret Detection, Dependency Scanning, or other info into this view, like the ability to open the vulnerability details modal or the ability to comment. The idea is that we can:

1. gain familiarity with the current implementation
2. make improvements to the existing UI, based on Becka's designs
3. set ourselves up to incorporate security findings in the same view