feat(core): Add TestBed.typedGet

[Goodwine]

TestBed.typedGet is a non breaking change to make way for a typed
TestBed.get signature. This commit adds the function with a different
name and strong types.

A future commit for Angular 9.x will replace the current TestBed.get
signature with the one added here, and TestBed.typedGet will be then
marked as deprecated to be completly removed on Angular 10.x

Injector.get will match the same signature as TestBed.typedGet on
Angular 9.x, both being breaking changes added at the same time.

Issue #26491
Fixes #29905

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

TestBed.get returns any

Issue Number: #26491

What is the new behavior?

TestBed.typedGet<T> returns T

Does this PR introduce a breaking change?

• Yes
• No

Other information

This is pre-work for a future breaking change where TestBed.get will no longer return any

[Goodwine]

After discussing with Vikram, I'm closing this for #32200

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