(#18458) Make Ruby DSL manifests always reload.

Ideally it should be possible to cache Ruby DSL manifests and reload on
demand when a change is detected. Other issues prevent this at the
moment.

This change adds the ability to watch a file with an "always stale"
option. This ensure that the cached environment will be recomputed the
next time an agent checks in.

The "always stale" option is used at the two locations where a Ruby DSL
is parsed (for the site manifest, and when loading types).
(#18739) Make calling functions from Ruby DSL work.

The implementation called a function such as "include" on the scope,
when it should have used "function_include". It also did not pass
arguments in an array as expected by the scope.
(#18458) Add test that "always stale" mode is supported for LoadedFile.

This checks that the always stale mode for LoadedFile works.
Later, this test (and the implementaton) may be removed as it is the
intent to also be able to only do on demand reparsing of Ruby DSL.
(#18458) Fix comment typos and removes unwanted required file.

This fixes typos in comments and instead of just copying the same text
in two location, there is now an updated explanation for what needs to
be checked later in the typeloader case. The two locations "compiler"
and "type_loader" now cross reference each other in the comments.

An unused require was also removed.
(#18458) Refactor "always-stale" LoadedFile into separate class.

This refactors the always-stale functionality in LoadedFile by creating
a derived class LoadedFileAlwaysStale and changing the initialization
signature back to the original.

The branch point in type_collection now picks the always-stale class if
passed true. 

The loadedfile_spec is consequently changed back, a separate test added
for LoadedFileAlwaysStale, and example cases added to
type_collection_spec (to check if it picks the regular or the always
stale implementation based on the passed flag).
(yardoc) Fix yardoc comments and others after always-stale refactoring

Some yardoc and regular comments did not reflect the change after the
refactoring. 

Also corrects non intentional removal of empty line (debugging cruft).
(#18458) Remove unnecessary test in always stale spec.

Test example now removed in favor of a comment pointing to contrasting
test for LoadedFile.
Merge pull request #1419 from hlindberg/18458-Reload-Ruby-DSL

18458, 18739 reload ruby dsl, make function call work