gccrs: Remove HIR::ForLoopExpr

gccrs: Remove HIR::ForLoopExpr

This will end up getting desugared into a LoopExpr with a MatchExpr body.

gcc/rust/ChangeLog:

	* backend/rust-compile-block.h: remove HIR::ForLoopExpr
	* backend/rust-compile-expr.h: likewise
	* checks/errors/privacy/rust-privacy-reporter.cc (PrivacyReporter::visit): likewise
	* checks/errors/privacy/rust-privacy-reporter.h: likewise
	* checks/errors/rust-const-checker.cc (ConstChecker::visit): likewise
	* checks/errors/rust-const-checker.h: likewise
	* checks/errors/rust-unsafe-checker.cc (UnsafeChecker::visit): likewise
	* checks/errors/rust-unsafe-checker.h: likewise
	* checks/lints/rust-lint-marklive.h: likewise
	* hir/rust-ast-lower.cc (ASTLoweringExprWithBlock::visit): likewise
	* hir/rust-hir-dump.cc (Dump::visit): likewise
	* hir/rust-hir-dump.h: likewise
	* hir/tree/rust-hir-expr.h (class ForLoopExpr): likewise
	* hir/tree/rust-hir-full-decls.h (class ForLoopExpr): likewise
	* hir/tree/rust-hir-visitor.h: likewise
	* hir/tree/rust-hir.cc (ForLoopExpr::as_string): likewise
	(ForLoopExpr::accept_vis): likewise
	* typecheck/rust-hir-type-check-expr.h: likewise

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