`ngc` would look for flat module resources relative to the flat module index.
`ngc` now looks for flat module resources relative to the `.d.ts` file that declarates
the component.
Fixes#15221
PR Close#15367
Inlcuded fixes:
- include preamble in generated source map
- always add a mapping for line/col 0 so that the
generated sourcemap is not sparse
- use a uniue sourceUrl for inline templates even
in the AOT case
