S528-016 deactivate diagnostics by default

[setton]

Create a trace, turned off by default, which controls the
emission of diagnostics.

To support testing diagnostics even if this feature is
swiched off:

• add a mechanism which accepts a ".gnatdebug" in the current
  dir to specify traces, overriding ~/.als/traces.cfg
• add a .gnatdebug activating the diagnostics trace in the
  test ada_lsp/publish_diag
• modify the Makefile to run each test in its directory,
  so that there can be local .gnatdebug files for each tests.

[raph-amiard]

I'm really not fond of using traces in the ALS to activate/deactivate features.

1. First [opinion] because traces are not meant for that IMHO, and it's just a weird GPS idiom to use the trace file to also be a config file, rather than you know, use a config file

2. Second, because it will be unintuitive to reactivate. For me you should have a default (here probably deactivate diagnostics) that you can reactivate via a setting in the configChanged request.

Ideally, after a few small fixes to diagnostics, that I have locally, I would even prefer that diagnostics are on by default but deactivated from the GPS side, because the decision to not have diagnostics is more of a GPS one than an ALS one (eg. they are pretty usable in VS Code IMO)

[setton]

I'm really not fond of using traces in the ALS to activate/deactivate features.

1. First [opinion] because traces are not meant for that IMHO, and it's just a weird GPS idiom to use the trace file to also be a config file, rather than you know, use a config file
2. Second, because it will be unintuitive to reactivate. For me you should have a default (here probably deactivate diagnostics) that you can reactivate via a setting in the configChanged request.

OK, I will add support for the configuration request. I will keep the code to activate "local traces" active, since this can be very useful, in particular for developers.

Ideally, after a few small fixes to diagnostics, that I have locally, I would even prefer that diagnostics are on by default but deactivated from the GPS side, because the decision to not have diagnostics is more of a GPS one than an ALS one (eg. they are pretty usable in VS Code IMO)

Right.