gccrs: Fix bad handling for recursive type query

gccrs: Fix bad handling for recursive type query

When resolving a type like this which is generic it causes the argument
substitution to go through bounds checking which is expected. But this
can call a type bounds probe which again calls a type query which will be
on the Impl Type on an impl block which can result in a recursive type
query which does eventually get caught and errors correctly. But this then
triggers some old error diagnositcs which are not valid error codes but old
error messages we used to catch simple errors very early on which do not
apply for this senario.

Fixes Rust-GCC#2905

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-item.cc (TypeCheckItem::resolve_impl_block_substitutions):
	dont check for unconstrained when the self is not resolved
	* typecheck/rust-hir-type-check-type.cc (TypeCheckType::resolve_root_path):
	remove bad debug error diagnostic
	* typecheck/rust-tyty-subst.cc: likewise

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: nr2 cant handle this
	* rust/compile/issue-2905-1.rs: New test.
	* rust/compile/issue-2905-2.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>