When computing the dependencies between packages which are not in
node_modules, we may need to rely upon path-mappings to find the path
to the imported entry-point.
This commit allows ngcc to use the path-mappings from a tsconfig
file to find dependencies. By default any tsconfig.json file in the directory
above the `basePath` is loaded but it is possible to use a path to a
specific file by providing the `tsConfigPath` property to mainNgcc,
or to turn off loading any tsconfig file by setting `tsConfigPath` to `null`.
At the command line this is controlled via the `--tsconfig` option.
Fixes#36119
PR Close#36180
380de1e7b4