Refactor InlineFindings to popover

What does this MR do and why?

This MR is meant to solve: #417007 (closed)

It refactors the MR Diff inline findings component to match the Design in:

And introduces the usage of the GitLabUI Popover Component: #415112[Changes_-_code_quality_dropdown.png]

Screenshots or screen recordings

with sast_reports_in_inline_diff false

no visual changes

Before
MR1_flag_off_before

with sast_reports_in_inline_diff true

inline findings are shown in dropdown

Before	After
MR1_flag_on_after	2023-08-07_21-11-51

with sast_reports_in_inline_diff true

Demo in side-by-side view

Demo
2023-08-08_11-03-05

How to set up and validate locally

1. Enable sast_reports_in_inline_diff
2. Make sure your running an ultimate license or your GDK (how to)
3. Clone this repo: https://gitlab.com/jannik_lehmann/code-quality-test
4. Recreate this MR: jannik_lehmann/code-quality-test!4 (diffs)
5. Let the pipeline finish and the go checkout the diff page for the restyled inline findings.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.