ScalaCLI should accumulate warnings about using experimental directives

[lwronski]

Is your feature request related to a problem? Please describe.
1.0.2

Describe the solution you'd like
Generated warnings should be cumulative, containing every experimental directives in a single warning message

Describe alternatives you've considered

For example, when using publish directives, ScalaCLI generates multiple warnings with almost identical messages:

The `//> using publish.developer "scala-cli"` directive is experimental.
Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
The `//> using publish.license "scala-cli"` directive is experimental.
Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
The `//> using publish.computeVersion "git:tag"` directive is experimental.
Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
The `//> using publish.repository "central"` directive is experimental.
Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli

Instead of the previous warnings, the output should look like this:

The directives:
  `//> using publish.developer "scala-cli"` 
  `//> using publish.license "scala-cli"`
  `//> using publish.computeVersion "git:tag"` 
  `//> using publish.repository "central"` are experimental.
Please bear in mind that non-ideal user experience should be expected.
If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli

[MaciejG604]

Done in #2376