Change annotations to use a NamedTuple (#55741)
Due to popular demand, the type of annotations is to be changed from a
`Tuple{UnitRange{Int}, Pair{Symbol, Any}}` to a `NamedTuple{(:region,
:label, :value), Tuple{UnitRange{Int}, Symbol,
Any}}`.
This requires the expected code churn to `strings/annotated.jl`, and
some changes to the StyledStrings and JuliaSyntaxHighlighting libraries.
Closes #55249 and closes #55245.
