Implement a simple cli debugging command

[expipiplus1]

It would be super useful to have an argument in hie which when passed causes hie to start, load the project, typecheck files, report any errors and exit. This would allow one to diagnose problems with hie's operation without setting up a lsp client.

Observe a run on ghcide with no arguments:

 $ ghcide
Starting ghcide (GHC v8.6)
/home/j/projects/upfind
[1/6] Finding hie-bios cradle
Cradle {cradleRootDir = "/home/j/projects/upfind", cradleOptsProg = CradleAction: default}

[2/6] Converting Cradle to GHC session

[3/6] Initialising IDE session

[4/6] Finding interesting files
Found 2 files

[5/6] Setting interesting files
[DEBUG] Set files of interest to: [NormalizedFilePath "./Setup.hs",NormalizedFilePath "./src/Main.hs"]
[DEBUG] Starting shakeRun (aborting the previous one took 0.00s)

[6/6] Loading interesting files
[DEBUG] Finishing shakeRun (took 0.00s, exception: thread killed)
[DEBUG] Starting shakeRun (aborting the previous one took 0.00s)
[DEBUG] Finishing shakeRun (took 0.15s, completed)
Files that worked: 2
Files that failed: 0
Done

The most important parts of this output to me are:

• The root directory
• The files of interest
• The number of working and failed files

It might be the case that this already exists, if so then it would be great to:

• Document this in the readme alongside searchable words like "debug" and "cli"
• Document this in hie --help

[alanz]

It just struck me that now that we have removed the jsonstdio transport, we were considering removing the --lsp flag. This broke clients, so we put it back as a no-op.

Perhaps if --lsp is not set, we should run in the CLI diagnostic mode. This will be the logical behaviour for people just having installed it.

[alanz]

And I notice the --lsp flag is what ghcide does too.

[fendor]

Enhanced by #1569
Now the functionality mirrors more the behaviour of ghcide, although since our internals are very different, the output is also different. In particular, we are way more verbose, and I hope that this will prove useful in debugging.

[expipiplus1]

Thanks!