gccrs: resolve: Add mappings for proc macros and resolving

gccrs: resolve: Add mappings for proc macros and resolving

Add multiple mappings for procedural macro name resolution.
Procedural macros were not resolved using name resolution and mapping
but rather with some hacky path comparison.

gcc/rust/ChangeLog:

	* expand/rust-macro-expand.cc (MacroExpander::import_proc_macros):
	Remove function.
	* expand/rust-macro-expand.h (struct MacroExpander): Remove
	import_proc_macro function.
	* util/rust-hir-map.cc (Mappings::insert_derive_proc_macro_def):
	Add a function to insert a derive proc macro definition.
	(Mappings::insert_bang_proc_macro): Remove function.
	(Mappings::insert_bang_proc_macro_def): Add function to insert a
	bang proc macro definition.
	(Mappings::insert_attribute_proc_macro_def): Likewise with
	attribute proc macros.
	(Mappings::lookup_derive_proc_macro_def): Add a function to
	lookup a defined derive proc macro definition.
	(Mappings::lookup_bang_proc_macro): Remove function.
	(Mappings::lookup_bang_proc_macro_def): Add a function to lookup
	a bang proc macro definition.
	(Mappings::lookup_attribute_proc_macro_def): Add a function to
	lookup an attribute prod macro definition.
	(Mappings::insert_derive_proc_macro_invocation): Add a function
	to insert a derive proc macro invocation.
	(Mappings::lookup_derive_proc_macro_invocation): Add a function
	to lookup a derive proc macro invocation.
	(Mappings::insert_bang_proc_macro_invocation): Add a function to
	insert a bang proc macro invocation.
	(Mappings::lookup_bang_proc_macro_invocation): Add a function to
	lookup a bang proc macro invocation.
	(Mappings::insert_attribute_proc_macro_invocation): Add a
	function to insert an attribute proc macro invocation.
	(Mappings::lookup_attribute_proc_macro_invocation): Add a
	function to lookup an attribute proc macro invocation.
	* util/rust-hir-map.h: Add different proc macro mappings
	and change function prototypes.
	* expand/rust-expand-visitor.cc (get_traits_to_derive): Return a
	vector of SimplePath instead.
	(derive_item): Accept SimplePath instead of a string.
	* ast/rust-ast.h: Add common ProcMacroInvocable interface to
	Identifiers and SimplePath nodes.
	* ast/rust-ast.cc: Add const modifier.
	* ast/rust-macro.h: Change path and identifier getters.
	* ast/rust-path.h: Change return type to reference.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>