Test infrastructure for plugins

[jneira]

• From Split HLS plugins into internal libraries #421: there is a friction for testing plugins that may live outside this repo. Now hls does not offer any test library to be used in those plugins, so functional tests must live in this repo (or it needs to be copied)

• From a comment of the referenced issue:

I can think off in some paths:

• move test infrastructure into hls-plugin-api if possible to avoid copy it in each plugin
  • to avoid create another package hls-plugin-api-test
• depend at runtime on hls executable without having it as component of the package (i think it should be possible somehow, but i have not checked it)
  • or create a dummy lsp server plugin container and put it in hls-plugin-api (or in lsp-test @bubba?)

We always could let the funcional tests live in hls, at least temporary, while we find out a final solution.

[jneira]

Thanks to @pepeiborra plugins can have their isolate functional test suite. Relevant pr's:

• Extract an hls-brittany-plugin package #1422: splitting brittany as a package with its test suite, moved from the hls global one
• Move tactics tests to be standalone #1425: moving test suite of tactics plugin
• Default main for ghcide  #1338: changes in ghcide main that enabled the possibility of split tests suites

Closing