build: update to typescript v3.8

[devversion]

Updates to TypeScript v3.8. To ensure that Angular Components is still
compatible with older supported TypeScript versions, a new integration
test has been introduced.

Unlike in angular/angular, our packages have a lot more entry-points, so manually
creating files that import all entry-points for the compatibility test is not suitable. This
required a more dynamic and less verbose solution.

Also, audited all TypeScript AST work to check for the new AST changes from v3.8. It looks like there is no action needed, but the class-name ng-update rule seems to need a general cleanup to handle namespaced exports/imports better. Added a comment w/ JIRA ticket.

[jelbourn]

Is there a way we could consolidate on a single, canonical list of packages for the repo? Right now I think there's a handful of places that need to be updated when we add a new package. Either that, or just documenting all the places that need to be updated

[devversion]

💯 Definitely agreed. I've been trying to reduce this type of duplication (as seen with entry-points in the system config etc.).

I'll work on a follow-up that gives us a better list of release packages. The problem always comes from the fact that we can't easily access these variables outside of Bazel (e.g. in the release scripts).

[jelbourn]

LGTM

(other comment can be a follow-up)

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