fix: handle single file components move to output-dir W-17615754

[cristiand391]

What does this PR do?

Fixes project retrieve start --output-dir lala writing single-file components to lala/main/default instead of lala.

How does --output-dir works?

1. SDR does the retrieve, there's no local components to merge with so it writes them to <output-dir>/main/default
2. project retrieve start checks if SDR retrieved files, if so then moves them from <output-dir>/main/default to <output-dir and nukes main/default.

The bug was in step 2, the command was skipping the file move if less than 2 files were retrieved (leaving single-file components like GlobalValueSet in <output-dir>/main/default.

Testing

1. clone dreamhouse and create a scratch org
2. create a globalvalueset in the org: sf org open -p lightning/setup/Picklists/home
3. retrieve it to lala, see it being written to lala/main/default: sf project retrieve start -m GlobalValueSet --output-dir lala
4. retrieve an apex class, it has 2 files (cls and meta xml) and will trigger the file move (including globalvalueset): sf project retrieve start -m ApexClass:PagedResult --output-dir lala

The component/file response check was introduced here to fix a ENOENT err:
#1236

the change in this PR updates the check to skip the file move if all retrieves failed so it shouldn't cause a regression and also fixes the ENOENT error on +1 failures:

What issues does this PR fix or reference?

@W-17615754@
forcedotcom/cli#3177

[shetzel]

Code changes look good but I'd like to address 2 things found during QA/review:

1. The file path has an extra slash so the code should use a resolved path: E.g., "filePath": "<project-dir>/dreamhouse-lwc/output//flows/Create_property.flow-meta.xml"
2. There is no NUT that checks for the correct path. We can add one pretty easily to test/nuts/retrieve/metadata.nut.ts. Just after the 'should warn when nothing retrieved into output-dir and not throw ENOENT' test we can add something like:

it('should retrieve a single metadata file with correct path', async () => {
      const result = await testkit.retrieve({ args: '--metadata Flow:Create_property --output-dir myOutput' });
      expect(result?.status).to.equal(0);
      const retrieveResult = result?.result as unknown as RetrieveResultJson;
      expect(retrieveResult.success).to.equal(true);
      expect(retrieveResult.files).to.be.an('array').with.lengthOf(1);
      expect(retrieveResult.files[0].filePath).to.contain('dreamhouse-lwc/myOutput/flows/Create_property.flow-meta.xml');
});