[SYCL] Remove broken support for SYCL-1.2.1

[HPS-1]

This PR removes the support for broken SYCL 1.2.1 mode, which is a prerequisite task for PR https://github.com/intel/llvm/pull/13283.

Justifications for deleted test cases: *sycl/test/basic_tests/aliases-legacy.cpp is deleted as it's only testing legacy aliases in SYCL-1.2.1 (that no longer exist in SYCL 2020).

Notes: *SYCLVersionList in LangOptions.h is not used anywhere, still keeping it though. *CL_SYCL_LANGUAGE_VERSION was in SYCL-1.2.1 but no longer exist in SYCL 2020, removing it. (Replaced by SYCL_LANGUAGE_VERSION.) *Test cases intended fully/partially for SYCL 1.2.1 should be reomoved or revised. Part of this work has been done in this PR and a separate one https://github.com/intel/llvm/pull/13556. Below is a list of the remaining SYCL 1.2.1 tests to revise/remove:

• Clang :: CodeGenSYCL/intel-fpga-no-global-work-offset.cpp
• Clang :: CodeGenSYCL/intel-max-global-work-dim.cpp
• Clang :: CodeGenSYCL/launch_bounds_nvptx.cpp
• Clang :: CodeGenSYCL/num-simd-work-items.cpp
• Clang :: CodeGenSYCL/scheduler-target-fmax-mhz.cpp
• Clang :: CodeGenSYCL/sycl-multi-kernel-attr.cpp
• Clang :: SemaSYCL/check-notdirect-attribute-propagation.cpp
• Clang :: SemaSYCL/check-work-group-size-hint-host.cpp
• Clang :: SemaSYCL/intel-max-global-work-dim-device-ast.cpp
• Clang :: SemaSYCL/intel-max-work-group-size.cpp
• Clang :: SemaSYCL/intel-restrict.cpp
• Clang :: SemaSYCL/lb_sm_90_ast.cpp
• Clang :: SemaSYCL/num_simd_work_items.cpp
• Clang :: SemaSYCL/num_simd_work_items_ast.cpp
• Clang :: SemaSYCL/parallel_for_wrapper_attr.cpp
• Clang :: SemaSYCL/reqd-work-group-size-host.cpp
• Clang :: SemaSYCL/reqd_work_group_size.cpp
• Clang :: SemaSYCL/scheduler_target_fmax_mhz_ast.cpp
• Clang :: SemaSYCL/sycl-2017-future-compat.cpp
• Clang :: SemaSYCL/sycl-esimd-ast.cpp
• Clang :: SemaSYCL/sycl-esimd.cpp

[elizabethandrews]

Am I understanding correctly that we are removing all support for SYCL 1.2.1 from our compiler? I don't think it is common practice to remove support for old versions of the standards. Can you please explain why we are?

Tagging @premanandrao for awareness

[premanandrao]

Am I understanding correctly that we are removing all support for SYCL 1.2.1 from our compiler? I don't think it is common practice to remove support for old versions of the standards. Can you please explain why we are?

Tagging @premanandrao for awareness

Thanks for the ping, @elizabethandrews. I second what @AlexeySachkov said above.

[elizabethandrews]

Am I understanding correctly that we are removing all support for SYCL 1.2.1 from our compiler? I don't think it is common practice to remove support for old versions of the standards. Can you please explain why we are? Tagging @premanandrao for awareness

Thanks for the ping, @elizabethandrews. I second what @AlexeySachkov said above.

I believe @AlexeySachkov 's comment has been resolved. Tests have been modified to use later standards as far as I can tell. I just found it strange we are removing entire support for older version of the standard. I didn't think that was common policy