Correct the generation of output file names for tsc --b

[sheetalkamat]

Fixes #30356

[RyanCavanaugh]

What's the diff other than the move?

[sheetalkamat]

To match what we do in getOwnOutputFileNames with sourceFile, eg. When file extension is JSON ignore everything else except it js output (that too only if its not same as input file name)
https://github.com/Microsoft/TypeScript/pull/30374/files#diff-20a9fa4d3e9d09f60c275a3dda245867R177

[weswigham]

@sheetalkamat is there something non-deterministic in this PR? We're failing on random versions of node with

        unittests:: tsbuild:: with resolveJsonModule option
           with resolveJsonModule and sourceMap:
     AssertionError: Diagnostic arrays did not match: expected [ Array(2) ] to deeply equal [ Array(2) ]