CRUD API for text

[pmconne]

Is your feature request related to a problem? Please describe.
The TextAnnotation2d and TextAnnotation3d elements provide a graphical representation of formatted text. Currently, there is no TypeScript API to create or manipulate that text in memory, nor read it from or write it to the iModel.

Describe the solution you'd like
A TypeScript API that provides the same capabilities as the C++ AnnotationTextBlock API, plus the ability to read+write the text to a text annotation element (via the AnnotationTextData aspect).

Describe alternatives you've considered
None.

Additional context
The C++ API is simplified from MicroStation, but still quite hairy. I see many opportunities to simplify it further for TypeScript. Cosmetically, I'd also like to remove the cumbersome "Annotation" prefix from all the type names.

We will need to implement an AnnotationTextStyle API as well. Ideally these will not be represented as elements, and we will prefer to obtain text styles from a workspace. We may not be able to get away with completely ignoring AnnotationTextStyle elements unfortunately, because connectors create them along with AnnotationTextData aspects that refer to them. But since data created by connectors should not be editable in other apps, we ought to be able to constrain the editing APIs to work only with workspace styles.