gccrs: Cleanup unused parameters to fix the bootstrap build

gcc/rust/ChangeLog:

	* backend/rust-compile-type.cc (TyTyResolveCompile::visit): Remove unused parameters.
	* backend/rust-constexpr.cc (constant_value_1): Likewise.
	(fold_non_dependent_init): Likewise.
	* backend/rust-tree.cc (publicly_uniquely_derived_p): Likewise.
	(instantiation_dependent_expression_p): Likewise.
	(type_has_nontrivial_copy_init): Likewise.
	(is_normal_capture_proxy): Likewise.
	(resolve_nondeduced_context): Likewise.
	(undeduced_auto_decl): Likewise.
	(require_deduced_type): Likewise.
	* checks/errors/privacy/rust-privacy-reporter.cc (PrivacyReporter::visit): Likewise.
	* checks/errors/privacy/rust-reachability.cc (ReachabilityVisitor::visit): Likewise.
	* checks/errors/privacy/rust-visibility-resolver.cc (VisibilityResolver::visit): Likewise.
	* checks/errors/rust-const-checker.cc (ConstChecker::visit): Likewise.
	* checks/errors/rust-unsafe-checker.cc (UnsafeChecker::visit): Likewise.
	* checks/lints/rust-lint-marklive.cc (MarkLive::go): Likewise.
	* checks/lints/rust-lint-unused-var.cc (unused_var_walk_fn): Likewise.
	* expand/rust-macro-builtins.cc (try_expand_single_string_literal): Likewise.
	(try_expand_many_expr): Likewise.
	(parse_single_string_literal): Likewise.
	(MacroBuiltin::assert_handler): Likewise.
	(MacroBuiltin::file_handler): Likewise.
	(MacroBuiltin::column_handler): Likewise.
	(MacroBuiltin::concat_handler): Likewise.
	(MacroBuiltin::env_handler): Likewise.
	(MacroBuiltin::line_handler): Likewise.
	* hir/rust-ast-lower-base.cc (ASTLoweringBase::visit): Likewise.
	(ASTLoweringBase::handle_doc_item_attribute): Likewise.
	* hir/rust-hir-dump.cc (Dump::visit): Likewise.
	* hir/tree/rust-hir-full-test.cc (ConstGenericParam::accept_vis): Likewise.
	* lex/rust-lex.cc (Lexer::parse_utf8_escape): Likewise.
	(Lexer::parse_string): Likewise.
	(Lexer::parse_char_or_lifetime): Likewise.
	* lex/rust-lex.h: Likewise.
	* metadata/rust-export-metadata.cc: Likewise.
	* resolve/rust-ast-resolve-expr.cc (ResolveExpr::visit): Likewise.
	* resolve/rust-ast-resolve-type.cc (ResolveType::visit): Likewise.
	(ResolveTypeToCanonicalPath::visit): Likewise.
	* resolve/rust-ast-verify-assignee.h: Likewise.
	* resolve/rust-early-name-resolver.cc (EarlyNameResolver::visit): Likewise.
	* typecheck/rust-hir-type-check-expr.h: Likewise.
	* typecheck/rust-hir-type-check-item.h: Likewise.
	* typecheck/rust-hir-type-check-pattern.cc (TypeCheckPattern::visit): Likewise.
	* typecheck/rust-tyty-rules.h: Likewise.
	* util/rust-attributes.cc (AttributeChecker::visit): Likewise.