Save args in run_results.json

[gshank]

resolves #2510

Description

Save cli arguments (or the equivalent for the RPC server) to run_results.json

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.

[gshank]

RPC run_results args with just 'run':
"args": {
"log_format": "default",
"write_json": true,
"profiles_dir": "/Users/gerda/.dbt",
"use_cache": true,
"host": "0.0.0.0",
"port": 8580,
"version_check": true,
"which": "rpc"
}

cli dbt run_results args with just 'run':
"args": {
"log_format": "default",
"write_json": true,
"profiles_dir": "/Users/gerda/.dbt",
"use_cache": true,
"version_check": true,
"which": "run",
"rpc_method": "run"
}

[jtcohen6]

Everything working as expected.

It does seem odd to me that the RPC run method returns {"which": "rpc"}, whereas CLI dbt run returns {"which": "run", "rpc_method": "run"}. That's a matter out of scope for this particular issue, but worth addressing when we eventually get around to RPC <> CLI consistency.

[gshank]

I found the "which" and "rpc_method" thing a bit odd too. I looked into it, and the code has a bunch of methods specifying both in the CLI version (not the rpc code, which. has only the one that's been passed to it). And I wasn't quite sure of the purpose and wasn't sure if we'd lose information by removing, so I left it there.

[jtcohen6]

Yeah... I would like to rationalize those someday, but it's not in scope for this issue per se.