Unwrap Constraints objects.  I don't actually think it's possible
to pass a Constraints object to this constructor, but there were
multiple places that kept testing children of this object.  I
*think* they were just being defensive, but I have no idea.

I know, it's crazy.

this also changes the constructor.  We don't need to pass more options
than "defaults" (whatever defaults are, ugh. probably another hash of
stupid stuff).

no need for redefine_method

Since `:shallow` may be set at any point in the resource nesting we should
only make the new and collection routes shallow when the parent is shallow.

This is a bit of a hack but until the mapper is refactored to an object graph
instead of a hash of merged values it's the best we can do.

Fixes #14684.

THe match documentation doesn't mention any requirement of the
parameter name requirement for matches. However, including a
bare glob character without a variable assignment causes a
parse error.

The method `shallow?` returns false if the parent resource is a singleton so
we need to check if we're not inside a nested scope before copying the :path
and :as options to their shallow equivalents.

Fixes #14388.

If the options :shallow_prefix and :shallow_path are not set in the
scope options then copy them from the normal :as and :path options
if they are set.

If a developer has specified either :path or :as in the options hash then
these should be used as the defaults for :shallow_path and :shallow_prefix.

Fixes #14241.

By tracking the depth of resource nesting we can push the need for nested
shallow scoping to only those routes that are nested more than one deep.
This allows us to keep the fix for #12498 and fix the regression in #14224.

Fixes #14224.

Originally with_scope_level was exclusively for managing scope levels with
resources, however it is now used for other things so it makes more sense
to move the responsibility for setting the :scope_level_resource to the
resource_scope method. This eliminates repeatedly setting it to the same
resource as each resource method scope is evaluated.

If we set :shallow_path when shallow is called it can result in incorrect
paths if the resource is inside a namespace because namespace itself sets
the :shallow_path option to the namespace path.

We fix this by removing the :shallow_path option from shallow as that should
only be turning shallow routes on and not otherwise affecting the scope.
To do this we need to treat the :shallow option to resources differently to
other scope options and move it to before the nested block is called.

This change also has the positive side effect of making the behavior of the
:shallow option consistent with the shallow method.

Fixes #12498.

Fixes #13824