gccrs: Refactor HIR::PatternItem class and its derivatives

gccrs: Refactor HIR::PatternItem class and its derivatives

Renames HIR::TupleItems to PatternItems for better generalization because it will be reused for
SlicePattern in the future. Enum values MULTIPLE/RANGED are renamed to NO_REST/HAS_REST
to reduce misleadingness as it is completely different and separate from the ranged values  `..`
representation. This results in renaming of all related classes and updates to all code that
references them.

gcc/rust/ChangeLog:

	* hir/tree/rust-hir-pattern.h:
		- Rename TupleItems to PatternItems.
		- Rename TuplePatternItemsMultiple/Ranged & TupleStructItemsRange/NoRange to
		TuplePatternItemsNoRest/HasRest and TupleStructItemsNoRest/HasRest.
		- Update enum values to NO_REST/HAS_REST.
		- Rename clone_tuple_items_impl to clone_pattern_items_impl.
	* hir/tree/rust-hir-full-decls.h: Renamed the classes accordingly.
	* hir/tree/rust-hir-visitor.h: Renamed the classes accordingly.
	* hir/tree/rust-hir-visitor.cc: Renamed the classes accordingly.
	* hir/rust-hir-dump.h: Renamed the classes accordingly.
	* hir/rust-hir-dump.cc: Renamed the classes accordingly.
	* hir/tree/rust-hir.cc: Renamed the classes accordingly.
	* hir/rust-ast-lower-base.cc: Renamed the classes accordingly.
	* hir/rust-ast-lower-pattern.cc: Renamed the classes accordingly.
	* backend/rust-compile-pattern.cc: Renamed the classes accordingly.
	* backend/rust-compile-var-decl.h: Renamed the classes accordingly.
	* checks/errors/borrowck/rust-bir-builder-pattern.cc: Renamed the classes accordingly.
	* checks/errors/borrowck/rust-bir-builder-struct.h: Renamed the classes accordingly.
	* checks/errors/borrowck/rust-function-collector.h: Renamed the classes accordingly.
	* checks/errors/rust-const-checker.cc: Renamed the classes accordingly.
	* checks/errors/rust-const-checker.h: Renamed the classes accordingly.
	* checks/errors/rust-hir-pattern-analysis.cc: Renamed the classes accordingly.
	* checks/errors/rust-hir-pattern-analysis.h: Renamed the classes accordingly.
	* checks/errors/rust-unsafe-checker.cc: Renamed the classes accordingly.
	* checks/errors/rust-unsafe-checker.h: Renamed the classes accordingly.
	* checks/errors/rust-readonly-check2.cc: Renamed the classes accordingly.
	* typecheck/rust-hir-type-check-pattern.cc: Update references to renamed classes and enum
	values.

Signed-off-by: Yap Zhi Heng <yapzhhg@gmail.com>