Improvements to dts emit for tsbuildinfo

[sheetalkamat]

1. Do not emit source maps when generating dts file
2. Json files from project reference should be able to do dts emit
3. Default if for any reason signature calculation fails should be source file version and exported modules from the file (just like what we do for d.ts file)

[weswigham]

We don't use the maps for LS results while project results are still pending, right?

[sheetalkamat]

This is strictly for builder which forces dts emit .. project if at all will always use declaration maps from disk and getting compile on save result is same as emit ( without forcing dts emit)