New plugin for annotated_text field type.
Largely a copy of `text` field type but adds ability to include markdown-like syntax in the text.
The “AnnotatedText” class parses text+markup and converts into plain text and AnnotationTokens.
The annotation token values are injected unchanged alongside the regular text tokens to provide a
form of additional indexed overlay useful in positional searches and highlighting.
Annotated_text fields do not support fielddata as we want to phase this out.
Also includes a new "annotated" highlighter type that retains annotations and merges in search
hits as additional annotation markup.
Closes#29467
markharwood