Add ls to RPC server

[iknox-fa]

resolves #3311 and #3356

Description

Adds support for the list method in the RPC server
Adds new keys for unique_id and original_file_path to list task when invoked with json output

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[jtcohen6]

This is working well for me in local testing!

A few comments:

• As I noted above, could we switch the type of select to accept a string as well as a list? It should work exactly the same as models and exclude
• For parity with the existing list task, I expected to see an error if models is set alongside select or resource_types, since these are mutually exclusive arguments. This shouldn't block merging the PR if it would be tricky to implement.
• The p0 resolution to Add keys to list output, parametrize #3356 is all we need for now. Could we open a new issue to capture the p1 requirement, parametrizing the set of returned keys?

[iknox-fa]

This is working well for me in local testing!

A few comments:

• As I noted above, could we switch the type of select to accept a string as well as a list? It should work exactly the same as models and exclude
  Done!
• For parity with the existing list task, I expected to see an error if models is set alongside select or resource_types, since these are mutually exclusive arguments. This shouldn't block merging the PR if it would be tricky to implement.
  Done!
• The p0 resolution to Add keys to list output, parametrize #3356 is all we need for now. Could we open a new issue to capture the p1 requirement, parametrizing the set of returned keys?
  Done!

[jtcohen6]

• There's one last failing test on Windows, I think because of file paths
• I confirmed that passing both models and select raises an error (good!), passing both resource_types params still doesn't raise the expected error ("models" and "resource_type" are mutually exclusive arguments). This isn't the most important thing: we're thinking of retiring the --models flag/param soon, anyway (Remove the distinction between --select and --models flags when working with node types #3210).

Once the failing test is sorted, I'm quite happy with where this is at. Nice work!

[iknox-fa]

• There's one last failing test on Windows, I think because of file paths
  Fixed!
• I confirmed that passing both models and select raises an error (good!), passing both resource_types params still doesn't raise the expected error ("models" and "resource_type" are mutually exclusive arguments). This isn't the most important thing: we're thinking of retiring the --models flag/param soon, anyway (Remove the distinction between --select and --models flags when working with node types #3210).
  Fixed!

Once the failing test is sorted, I'm quite happy with where this is at. Nice work!

[kwigley]

👍

[jtcohen6]

lgtm!