This can also be customized via the new method `resourceNameToFileName` in the `CompilerHost`.
This also allows to customize the filePaths in `.ngsummary.json` file via the new methods `toSummaryFileName` and `fromSummaryFileName` on the `CompilerHost`.
- remove unneeded methods (`getNgCanonicalFileName`, `assumeFileExists`) - simplify moduleName <-> fileName conversion logic as we don’t need to account for `genDir` anymore. - rename `createNgCompilerHost` -> `createCompilerHost`