Remove deprecated functionality from Angular code

[kaidohallik]

Overview of the feature request

I would like to remove deprecated functionality from Angular code. As replacing TestBed.get with TestBed.inject was bigger task (without using type casting as unknown workaround) then I create this ticket to track different PR-s:

• [x] replace TestBed.get with TestBed.inject

  • [x] replace other deprecated functionality

  • [ ] apply ESLint rule https://github.com/gund/eslint-plugin-deprecation to avoid further deprecated functionality

Motivation for or Use Case

As we are hipsters then we should avoid using deprecated functionality.

Related issues or PR

Starting with PR-s shortly.

• [x] Checking this box is mandatory (this is just to show you read everything)

[kaidohallik]

Bounty claimed https://opencollective.com/generator-jhipster/expenses/28313

[pascalgrimaud]

@kaidohallik : approved