fix: exclude specific folders from coverage

[stact]

Description
Hi team, we are not able exclude folders from coverage, I don't know if it's a bug, or
For instance we have generated folder that include our localization

`very_good test --coverage --exclude-coverage "lib/l10n/**"``

Steps To Reproduce

1. On your project folder create dummy folder with some dart files
2. Open a terminal
3. "cd" to your flutter project folder
4. Launch the coverage very_good test --coverage --exclude-coverage "lib/l10n/**"
5. See the results of the coverage (using vscode flutter coverage extension)

Expected Behavior
The folder excluded must be ignored for coverage

Screenshots

Additional Context
Tried also to ignore files directly it's not working too

[tomarra]

Hi @stact 👋 thanks for opening this issue. From a quick glance at this we were able to reproduce this so were going to look into the --exclude-coverage flag and it's implementation.

We are always willing to let contributors help with fixes as well. Would you be willing to help with this?

[stact]

Hi @tomarra thank you for reaching out
Unfortunately my knowledge is limited regarding coverage.
I was looking in the past some alternative, maybe this PR can help to adapt the vg test dart-archive/coverage#496

[stact]

Ok it seems something is wrong with very_good test --coverage firstly generated

This solution solved my issue VeryGoodOpenSource/very_good_cli#496 (comment)

lcov --remove coverage/lcov.info '**/generated/**' -o coverage/lcov.info

No problem also on ci.

build:
    uses: VeryGoodOpenSource/very_good_workflows/.github/workflows/flutter_package.yml@v1
    with:
      flutter_channel: stable
      coverage_excludes: "**/generated/**" 

Thank you for your followup @tomarra maybe it can be removed from the backlog