gccrs: Refactor AST Patterns that hold multiple pattern items

gccrs: Refactor AST Patterns that hold multiple pattern items

Patterns include TuplePattern, TupleStructPattern & SlicePattern. Besides making their pattern
items container class inherit from a common `PatternItems` base class just like in HIR for
better standardization, mentions of `Range` are also changed to `HasRest` or `NoRest`.

gcc/rust/ChangeLog:

	* ast/rust-pattern.h:
		- Add a new base abstract class `PatternItems` which are used by pattern items class
		class derivatives for `TuplePattern`, `TupleStructPattern` & `SlicePattern`.
		- Standardized the derived class names to have `HasRest` or `NoRest` as suffixes.
		 - Values for the common `ItemType` enum is updated to `HAS_REST` or `NO_REST`.
	* ast/rust-pattern.cc: Renamed the classes accordingly.
	* ast/rust-ast-collector.cc: Renamed the classes accordingly.
	* ast/rust-ast-collector.h: Renamed the classes accordingly.
	* ast/rust-ast-full-decls.h: Renamed the classes accordingly.
	* ast/rust-ast-visitor.cc: Renamed the classes accordingly.
	* ast/rust-ast-visitor.h: Renamed the classes accordingly.
	* ast/rust-desugar-for-loops.cc: Renamed the classes accordingly.
	* ast/rust-desugar-question-mark.cc: Renamed the classes accordingly.
	* expand/rust-cfg-strip.cc: Renamed the classes accordingly.
	* expand/rust-cfg-strip.h: Renamed the classes accordingly.
	* expand/rust-derive-clone.cc: Renamed the classes accordingly.
	* expand/rust-derive-cmp-common.cc: Renamed the classes accordingly.
	* expand/rust-derive-hash.cc: Renamed the classes accordingly.
	* expand/rust-derive-ord.cc: Renamed the classes accordingly.
	* expand/rust-derive-partial-eq.cc: Renamed the classes accordingly.
	* expand/rust-derive.h: Renamed the classes accordingly.
	* expand/rust-expand-visitor.cc: Renamed the classes accordingly.
	* expand/rust-expand-visitor.h: Renamed the classes accordingly.
	* hir/rust-ast-lower-base.cc: Renamed the classes accordingly.
	* hir/rust-ast-lower-base.h: Renamed the classes accordingly.
	* hir/rust-ast-lower-pattern.cc: Renamed the classes accordingly.
	* hir/tree/rust-hir-pattern.h: Renamed the classes accordingly.
	* parse/rust-parse-impl.h: Renamed the classes accordingly.
	* resolve/rust-ast-resolve-base.cc: Renamed the classes accordingly.
	* resolve/rust-ast-resolve-base.h: Renamed the classes accordingly.
	* resolve/rust-ast-resolve-pattern.cc: Renamed the classes accordingly.
	* util/rust-attributes.cc: Renamed the classes accordingly.
	* util/rust-attributes.h: Renamed the classes accordingly.

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