dynamic-require: fast path for re-exported variables

When `dynamic-require` is used to access an export that isn't a
variable defined in the same module, `dynamic-require` falls
back to `eval` in a fresh namespace, which can be expensive.
The new fast path handles the case that a variable is re-exported.

The new fast path is relevant to deserialization, which now
uses a submodule that re-exports from an enclosing module.
increase timeout of `raco exe` test suite
fix closure type tracking for a procedure with only an unused rest arg

Closes PR 14259
compiler/zo-structs: fix docs to note 'fixnum and 'flonum types
raco: use executable yield handler before existing

Makes `raco` wait as it should for a GUI tool.

Closes PR 14261
raco setup: fix corners where db might not exist

Using something like `raco pkg remove` in an incompletely
set up installation could lead to failures attempting to
access a database file that isn't there.