fix `expt` test

I think that the sign on `(expt -0.1 -100000000000000000001/3)` depends
too much on the precision of `expt` to be a good test, so just check
that the result is a complex number with infinite parts.
Fix prefix-out for identifiers with spaces
add tests for `prefix-in`, etc.
fix docs for `install-collection` "info.rkt" field

Closes PR 14831
Keep track of (and return) a list of modules (re)loaded during dynamic-rerequire
Fix doc for dynamic-rerequire
Fix error handling of parallel-compile-files.

Related to PR 14809.
fix doc typos
parallel-compile-files: fix docs and argument check for the handler callback
move `raco make` test to a more sensible place
explain the indentation preferences
Add struct inheritance in type-environment

Use it to start adding types for a subset of
typed/racket/sandbox
Avoid creating impersonators/chaperones when not required in struct/dc.