Migrate calls to the deprecated `Language` methods

[dtdesign]

There is currently still a significant usage of the legacy methods that have been deprecated in 6.0. They are bad from a DX perspective by not allowing for automated imports and the performance of addObject() is actually quite bad.

• [ ] Replace uses of get() with getPhrase().
• [ ] Replace uses of add() with registerPhrase() when the phrase requires extra parameters.
• [ ] Replace uses of addObject() with {jsphrase} or registerPhrase() (if it requires extra parameters).