refactor(core): Migrate TestBed.get to TestBed.inject

[Goodwine]

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?

Angular codebase uses TestBed.get

Issue Number: #26491

What is the new behavior?

Angular codebase uses TestBed.inject

Does this PR introduce a breaking change?

• Yes
• No

Other information

This PR depends on #32200 to be submitted

[Goodwine]

@mhevery Couple unrelated changes are - AIO angular version was bumped to 9.0.0.next.5 from 8.0.0.next.1, and the bundle size check was updated, IIRC some changes should make the bundle smaller due to better treeshaking so I thought it was fine, can these be added together or should the version bump be a separate PR?

[mhevery]

presubmit

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