Updates for all angular.io links to the new angular.dev domain. Additionally, adjustment to new resources where the equivalent does not exist on the new site (e.g. Tour of Heroes tutorial)
An internal schematics helper rule has been introduced for Angular schematics that only generate a set of project files from a set of templated files. Multiple current generation schematics contained essentially the same code which increased the sustainment burden and made refactoring and improvements more complicated.
Currently when using `ivy-ngcc` it will print out a warning
```
Failed to read entry point info from //node_modules/@schematics/angular/workspace/files/package.json with error SyntaxError: Unexpected token < in JSON at position 1121.
```
Fixes#13378
This aligns options that do the same thing:
1) `skipSpecs` and `spec` has been deprecated in favor of `skipTests`.
2) `styleext` has been deprecated in favor of `style` since the latest is two words.
Fixes#12784
