[SYCL][NFC] Drop on-device tests in favor of llvm-test-suite (intel#4393)

The original motivation for introducing on-device tests was two-fold:

- Provide a way to test product changes together with E2E test changes
for features in active development, these tests would then be moved to
llvm-test-suite once the feature is considered stable. Frequently,
instead of using on-device tests (or in case an existing llvm-test-suite
test has to be modified) developers would create a pull request in each
repo, link them via a comment, then they would be either merged
simultaneously (while relying on local testing and intel/llvm post-commit
results for the modified/added tests) or one after the other.
- As a way to have some sanity E2E checks in intel/llvm. On-device
tests haven't been used in this manner, we've been relying on component
tests instead.

This patch drops in-tree on-device tests in favor of llvm-test-suite
in order to reduce in-tree test running time.

Author: sergey-semenov

CONTRIBUTING.md

@@ -66,11 +66,6 @@ There are 3 types of tests which are used for DPC++ toolchain validation:
 should not have hardware (e.g. GPU, FPGA, etc.) or external software
 dependencies (e.g. OpenCL, Level Zero, CUDA runtimes). All tests not following
 this approach should be moved to DPC++ end-to-end or SYCL-CTS tests.
-However, the tests for a feature under active development requiring atomic
-change for tests and product can be put to
-[sycl/test/on-device](../../sycl/test/on-device) temporarily. It is developer
-responsibility to move the tests to DPC++ E2E test suite or SYCL-CTS once
-the feature is stabilized.
 
     **Guidelines for adding DPC++ in-tree LIT tests (DPC++ Clang FE tests)**:
     - Use `sycl::` namespace instead of `cl::sycl::`

sycl/test/CMakeLists.txt

@@ -105,4 +105,3 @@ if(SYCL_BUILD_PI_ROCM)
 
   add_dependencies(check-sycl check-sycl-rocm)
 endif()
-add_subdirectory(on-device)

sycl/test/lit.cfg.py

@@ -27,7 +27,7 @@
 config.suffixes = ['.c', '.cpp', '.dump'] #add .spv. Currently not clear what to do with those
 
 # feature tests are considered not so lightweight, so, they are excluded by default
-config.excludes = ['Inputs', 'feature-tests', 'on-device']
+config.excludes = ['Inputs', 'feature-tests']
 
 # test_source_root: The root path where tests are located.
 config.test_source_root = os.path.dirname(__file__)