fix(@schematics/angular): TypeScript related migrations should cater for BOM
In the CLI `UpdateRecorder` methods such as `insertLeft`, `remove` etc.. accepts positions which are not offset by a BOM. This is because when a file has a BOM a different recorder will be used https://github.com/angular/angular-cli/blob/master/packages/angular_devkit/schematics/src/tree/recorder.ts#L72 which caters for an addition offset/delta.
The main reason for this is that when a developer is writing a schematic they shouldn't need to compute the offset based if a file has a BOM or not and is handled out of the box.
Example
```ts
recorder.insertLeft(5, 'true');
```
However this is unfortunate in the case if a ts SourceFile is used and one uses `getWidth` and `getStart` method they will already be offset by 1, which at the end it results in a double offset and hence the problem.
Fixes#30713
PR Close#30719
In an Angular CLI project scenario where projects only reference
top-level source-files through the `tsconfig` `files` option, we currently
do not migrate referenced source-files. This can be fixed checking all
referenced source-files which aren't coming from an external library.
This is similar to how `tslint` determines project source-files.
PR Close#30269
Currently the injectable pipe schematic generates invalid imports like `import import { Pipe, PipeTransform, Injectable } from '@angular/core'; from '@angular/core';`. The issue wasn't caught by the unit tests, because the invalid import still contains the valid one.
Fixes#30159.
PR Close#30170
Alan Agius
Paul Gschwendtner
crisbeto