Implement project.watch configuration options

[matuszeman]

What this PR does / why we need it:

TODO

Which issue(s) this PR fixes:

Fixes #1269

TODO

[eysi09]

Hi @matuszeman!

Let me start by apologising for the late response. And follow up with a big thank you for the pull request!

The person you'd been in contact with is away on vacation so this one somehow fell in between the cracks. I'm really sorry for that.

I'm away myself until after the weekend but we'll get to this ASAP early next week.

[edvald]

Sorry I just got to this, back from vacation now. I think this is a good feature to add, but there's a bit of nuance to consider in the implementation.

A couple of points I see at first glance:

1. It might actually make sense to just use the modules.include/modules.exclude fields. We're only really watching for changes to modules, and the separate field is likely superfluous.
2. We can only in some cases apply the modules.include field as an optimization, which is when there are only specific directories listed under that field, or directories followed by globs. That's feasible to implement, but would need to be documented.
3. The exclude part should work mostly as-is, just needs a bit more work to handle configuration changes. We essentially will need to fully reset the watcher when we reconfigure. Shouldn't be hard though, and likely better to do that either way.
4. We would need to add some tests to make sure this all works as expected, but of course this is just a draft PR :)

@matuszeman would you like to carry on with this, or should I have a go?

[matuszeman]

You came and I'm leaving until Sunday :) so to move things forward I'd appreciate any help from your side if you find spare second.

I've been also thinking about implementing watch option on module level instead where it might make more sense maybe, and will be closer to the codebase of particular module, thus easier to manage.
modules on project level would be used to discover module garden files only and watch for those and module configuration would dictate what to watch on module level only. One module could be with NodeJS codebase where I'd definitely exclude node_modules or PHP with its vendor folder for example.

[edvald]

Closing in favor of #1320, but thanks so much @matuszeman for the contribution!