Use submodules instead of marking tricks for identifiers in docs.
Register scoped type variables for internal def. annotations.

Closes PR 13793.
Make resolve actually do all the necessary resolutions.
Centralize the definition of the plambda syntax property.
Centralized typechecker:ignore properties.
Consolidate the rest of the syntax properties in TR.
Make for loops in TR use an annotation when applicable.
Use in-syntax instead of in-list/syntax->list.
Add syntax-length to unstable/syntax.
Make TR use syntax-length instead of (length (syntax->list x)).
Move from syntax-map to stx-map.
Move from syntax->list and map to stx-map.
Add error checking to in-syntax.
Replace syntax-map with stx-map in unstable/automata
Replace syntax-map with stx-map in plai.
Use abbreviations for filters.
Share definition of erase-filter.
Removed unnecessary require.
Remove unused definition and clean up exports.
Remove syntax-map.