[Ada] New No_Local_Tagged_Types restriction

[Pierre-Marie de Rodat via Gcc-patches]

Add new configuration restriction No_Local_Tagged_Types. This new
restriction ensures at compile time that all tagged types are only
declared at the library level.

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

gcc/ada/

        * libgnat/s-rident.ads (Restriction_Id): Add
        No_Local_Tagged_Types, update comment for adding new GNAT
        specific restriction.
        * restrict.ads (Implementation_Restriction): Add
        No_Local_Tagged_Types.
        * sem_ch3.adb (Analyze_Full_Type_Declaration): Add check for
        tagged type at library level.
        * doc/gnat_rm/standard_and_implementation_defined_restrictions.rst:
        Add No_Local_Tagged_Types description.
        * gnat_rm.texi: Regenerate.

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