st/mesa: unify destroy_program_variants cases for TCS, TES, GS
st/mesa: unify destroy_program_variants cases for TCS, TES, GS

Reviewed-by: Edward O'Callaghan <117173807d5a49976a891944633465c0daea7f98@alterapraxis.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler