[Ada] Remove dependency on tampering checks and controlled types for formal

[Ada] Remove dependency on tampering checks and controlled types for formal

[Pierre-Marie de Rodat]

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Formal hashed sets and maps are now using a different type of hash table
that does not require controlled types. This is possible because formal
containers do not rely on tampering checks, as cursors do not hold a
pointer to a single matching container, but are logical indexes that can
be used with multiple containers.

For simplicity of the package organisation, and symmetry with other
versions of containers, add a formal version of hashed types in the
shared Ada.Containers.Hash_Tables unit. This unit should be specialized
to only include the formal version of hash tables for runtimes that
do not support controlled types (so that the dependency on
Ada.Containers.Helpers can be removed).

The new versions of units for generic keys and operations are modified
versions of the units for bounded containers, with all tampering checks
removed (they were no-op in formal containers). A declaration of
constant Checks is added at the start of the body, as these units cannot
use the version in Ada.Containers.Helpers.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* Makefile.rtl: Add new files.
	* libgnat/a-cfhama.adb: Use formal version of hash tables.
	* libgnat/a-cfhama.ads: Same.
	* libgnat/a-cfhase.adb: Same.
	* libgnat/a-cfhase.ads: Same.
	* libgnat/a-chtgfk.adb: New unit for formal containers, modified
	version of Generic_Bounded_Keys.
	* libgnat/a-chtgfk.ads: Same.
	* libgnat/a-chtgfo.adb: New unit for formal containers, modified
	version of Generic_Bounded_Operations.
	* libgnat/a-chtgfo.ads: Same.
	* libgnat/a-cohata.ads (Generic_Formal_Hash_Table_Types): Third
	version of the type for hash tables, equivalent to the bounded
	version without tampering checks.

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