gccrs: fix bug in pattern check for tuples

gccrs: fix bug in pattern check for tuples

We can point to generic parent types which means we need to do the shallow
resolve thing that rustc does. We have destructure which is similar to get
what the parameter type points to.

Fixes #2775

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::visit): use destructure

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2775.rs: New test.

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