[core] core plugins update

[yoannmoinet]

What and why?

Still building up #78 and trying to split it as much as possible to keep the review complexity down.

How?

This one can be summed up as:

• Some small config updates that were missed in previous PRs.
• Refactor of the internal plugin mechanism and move some types.
• Implementation of internal git plugin that adds some git metadata to the build.
• Update some test helpers.

[datadog-datadog-staging-us1-all]

Software Composition Analysis

We found vulnerabilities in the following libraries (compared a038785 against 85330b7):

• 🔴 braces@2.3.2 🆕
• 🔴 braces@3.0.2 🆕
• ⚫ webpack@5.1.3
• ⚫ json-schema@0.2.3
• ⚫ webpack@5.49.0
• 🔴 tar@6.0.2
• 🔴 qs@6.5.2
• 🔴 decode-uri-component@0.2.0
• 🔴 minimatch@3.0.4
• 🔴 semver-regex@2.0.0
• 🔗 7 more vulnerabilities exist

[elbywan]

LGTM 👍

[elbywan]

⛏️ small nit: I don't think this would be easy for a new contributor to understand that the code between these 2 markers gets replaced when the yarn cli integrity tool runs so it might be nice to add a comment or something?
Also I could not find in the contributing.md/readme.md a mention about when to run this tool (when adding a plugin?) but maybe it's not meant to be very often

[yoannmoinet]

Very good point, I'll update the doc(s) and add comments to give more details on this.