feat(TestBed): add whitespace handling to compile

Add whitespace handling to the TestBed’s compile function.

Closes #1262. Previously, strings passed with leading or
trailing whitespace would be compiled incorrectly. Now,
valid HTML with arbitrary whitespace in and surrounding it
can be compiled properly.

Closes #1346

Closes #1445
fix(components): TranscludingComponentFactory passes a wrong element to onShadowRoot

Closes #1435

Closes #1436
refactor(tests): replace deprecated `toThrow` with `toThrowWith`

Closes #1425