… be resolved

Rollup just prints a warning if an import cannot be resolved and ends up
being treated as an external dependency. This in combination with the
`silent = True` attribute for `rollup_bundle` means that bundles might
end up being extremely small without people noticing that it misses
actual imports.

To improve this situation, the warning is replaced by an error if
an import cannot be resolved.

This unveiles an issue with the `ng_rollup_bundle` macro from
dev-infra where imports in View Engine were not resolved but ended
up being treated as external. This did not prevent benchmarks using
this macro from working because the ConcatJS devserver had builtin
resolution for workspace manifest paths. Though given the new check
for no unresolved imports, this will now cause errors within Rollup, and
we need to fix the resolution. We can fix the issue by temporarily
enabling workspace linking. This does not have any performance
downsides.

To enable workspace linking (which we might need more often in the
future given the linker taking over patched module resolution), we
had to rename the `angular` dependency to a more specific one so
that the Angular linker could link into `node_modules/angular`.

We removed `bazel-toolchains` from the repository since dev-infra
provides the RBE platforms now (in a way where they are not reliant
on the Bazel version), so the comment in `.bazelversion` can be
removed.

Skydoc is no longer used as `@angular/bazel` is no longer a
public API. The Sass rules were only used in a single place
in the repo where Sass is not really needed and has just been
added by accident most likely. We want to remove the Sass dependency
in preparation for Rules NodeJS v4.x where the Sass rules currently
still use an older version of `@bazel/worker` that is incompatible.

This commit applies changes to `@angular/bazel` which are necessary
to support the Bazel NodeJS rules v4.0.0. The Bazel NodeJS rules
no longer support the `_tslibrary` option for the `LinkablePackageInfo`
provider and therefore we need to stop using it. Due to this removal,
we also need to add two new attributes called `package_name` and
`package_path` so that the API of `ng_module` matches `ts_library`.

Note: This is denoted as `refactor` as we currently are not able to
merge feature commits into patch branches, but we want the tooling
to not diverge significantly between the patch and next branch. It is
planned to update the merge tooling to allow for such changes to land.

Updates the Bazel NodeJS rules to v4.0.0-beta.0. This is necessary
so that the Angular components repo can update, and it's generally
good to stay as up-to-date as possible with the Bazel rules as it's
easy to fall behind, and updating early allows us to discover issues
affecting our tooling earlier (where they are easier to address due to
e.g. potential breaking change policy).