build: fix failing nightly snapshot tests

[devversion]

Apparently Yarn installs mismatching dependencies of Angular Github snapshot packages. Meaning that we need to flatten out all dependencies for @angular/* packages.

This can be achieved by using the Yarn's resolutions feature.

[devversion]

Note: The size change seems unrelated. This PR is rebased on top of master. Maybe the size baseline hasn't been saved in master properly.

[jelbourn]

LGTM

[ngbot]

I see that you just added the pr: merge ready label, but the following checks are still failing:
     status "ci/angular: size" is failing
     status "ci/circleci: tests_browserstack" is pending
     status "ci/circleci: tests_saucelabs" is pending

If you want your PR to be merged, it has to pass all the CI checks.

If you can't get the PR to a green state due to flakes or broken master, please try rebasing to master and/or restarting the CI job. If that fails and you believe that the issue is not due to your change, please contact the caretaker and ask for help.

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