Add common parts for vextublx class extract instructions for P9.

[munroesj52]

Add common operations for the
Vector Extract Unsigned to GPR using GPR-specified Left/Right-Index class instructions.
These implement the ISA equivalent operations without PVIPR bi-endian transforms imposed by the vec_extract intrinsic.
These can then be used to implement the equivalent bi-endian vec_extract operations for __ARCH_PWR7/8 not supported by compilers. Or other cases where the raw ISA operation is needed (without PVIPR transforms).

* src/pveclib/vec_common_ppc.h
- (vec_vextublx_PWR7, vec_vextublx_PWR9): New common operations for vextublx.
- (vec_vextubrx_PWR7, vec_vextubrx_PWR9): New common operations for vextubrx.
- (vec_vextuhlx_PWR7, vec_vextuhlx_PWR9): New common operations for vextuhlx.
- (vec_vextuhrx_PWR7, vec_vextuhrx_PWR9): New common operations for vextuhrx.
- (vec_vextuwlx_PWR7, vec_vextuwlx_PWR9): New common operations for vextuwlx.
- (vec_vextuwrx_PWR7, vec_vextuwrx_PWR9): New common operations for vextuwrx.

* src/testsuite/arith128_test_char.c (test_vextub_indexed): New functional test for vextublx/vextubrx.
- (test_vextuh_indexed): New functional test for vextuhlx/vextuhrx.
- (test_vextuw_indexed): New functional test for vextuwlx/vextuwrx.
- (test_vec_char): Add functional tests to test driver.

* src/testsuite/vec_char_dummy.c (test_mfvsrwz, test_mfvrd): Compile tests for mfvsrwr and mfvrd.
- (test_vec_vextublx, test_vec_vextubrx): Common operation compile tests.
- (test_vec_vextuhlx, test_vec_vextuhrx): Common operation compile tests.
- (test_vec_vextuwlx, test_vec_vextuwrx): Common operation compile tests.
- (test_vextublx_V0, test_vextuhlx_V0, test_vextublx_V0): Implementation compile tests.
- (test_vextubrx_V0, test_vextuhrx_V0, test_vextubrx_V0): Implementation compile tests.

* src/testsuite/vec_pwr9_dummy.c
- (test_vec_vextublx_PWR9, test_vec_vextubrx_PWR9): Common operation compile tests.
- (test_vec_vextuhlx_PWR9, test_vec_vextuhrx_PWR9): Common operation compile tests.
- (test_vec_vextuwlx_PWR9, test_vec_vextuwrx_PWR9): Common operation compile tests.