Extract common code to dedicated GitHub actions and fail the build if the lock file is not up-to-date

[caponetto]

What changes were proposed in this pull request?

In this PR:

• Extract Yarn installation to a dedicated action. This will facilitate future upgrades.
• Install UI dependencies using a dedicated action that also checks whether the lock file is up-to-date or not.

How was this pull request tested?

I've tested it on my fork. When the lock file is not up-to-date, the UI-related jobs fail.

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[caponetto]

@lresende This is a small improvement to protect us against a dirty lock file.