chore: updates coverage GH action to compare coverage against base branch

[0xItadaki]

1- When the PR is created, it runs the coverage in the base branch and caches result
2- With every push it calculates the coverage in the current PR and creates a comment with coverage information. This comment is updated every time there is a new push.

3- It compares the total coverage from the base branch and the new push. If the coverages decreases in the new push, a the comment is updated and the build fails

Note: yarn coverage only runs unit tests to avoid killing the RPC with fuzz tests
Note: It uses a sensitivity factor, otherwise the coverage fails even if nothing changes.

[github-actions]

LCOV of commit 17a74e0 during Coverage Check #149

Summary coverage rate:
  lines......: 67.0% (75 of 112 lines)
  functions..: 62.5% (15 of 24 functions)
  branches...: 100.0% (14 of 14 branches)

Files changed coverage rate: n/a