fix(ng-update): migrations not running for release candidate versions

[devversion]

7a433f6 set up the migrations for v9, but we actually forgot
that we want to run migrations in the next and RC versions too.

[devversion]

I pushed a second commit that validates the migration collection as part of CI, staging and releasing.

[andrewseguin]

LGTM - pending Miles' comment, I'll merge in and get the RC going

[sawyerbutton]

Any hint about how material fix

Increased main.js bundle size but less lazy chunks after updating to angular 9.0.0-rc.1 #16146

problem?

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