TitleFormatter should extend StringFormatter

Problem/Motivation

TitleFormatter currently extends from BasicStringFormatter. However StringFormatter would be a much better starting point as it already has one of the settings that TitleFormatter is adding.

The code in StringFormatter has some improvements

1. Doesn't force the link render array to string in viewElements().
2. Correctly handles revisions.

Unfortunately the setting in StringFormatter has a different name: link_to_entity instead of linked.

Proposed resolution

1. Change TitleFormatter to extend StringFormatter.
2. Write an update hook to fix the setting name in existing display settings.

Remaining tasks

User interface changes

Slight differences in formatter settings.

API changes

None

Data model changes

Change of formatter setting name link_to_entity instead of linked.