Refactor wimpy feature (#2507)

- Make it a common parameter in harness using either '-w', '--wimpy' or
'CL_WIMPY_MODE' environment variable.
- Remove all test specific wimpy variable.

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Co-authored-by: Kévin Petit <kpet@free.fr>

test_common/harness/parseParameters.h

@@ -41,6 +41,7 @@ extern std::string gCompilationProgram;
 extern bool gDisableSPIRVValidation;
 extern std::string gSPIRVValidator;
 extern bool gListTests;
+extern bool gWimpyMode;
 
 extern int parseCustomParam(int argc, const char *argv[],
                             const char *ignore = 0);