[clang][OpenMP] Place some common code in functions (#96811)

There are chunks of code repeated in a number of functions. This patch
moves some of that code into individual functions.

Author: kparzysz

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -11180,16 +11180,12 @@ def err_omp_several_directives_in_region : Error<
 def note_omp_previous_directive : Note<
   "previous '%0' directive used here">;
 def err_omp_sections_not_compound_stmt : Error<
-  "the statement for '#pragma omp sections' must be a compound statement">;
-def err_omp_parallel_sections_not_compound_stmt : Error<
-  "the statement for '#pragma omp parallel sections' must be a compound statement">;
+  "the statement for '#pragma omp %0' must be a compound statement">;
 def err_omp_orphaned_section_directive : Error<
   "%select{orphaned 'omp section' directives are prohibited, it|'omp section' directive}0"
   " must be closely nested to a sections region%select{|, not a %1 region}0">;
 def err_omp_sections_substmt_not_section : Error<
-  "statement in 'omp sections' directive must be enclosed into a section region">;
-def err_omp_parallel_sections_substmt_not_section : Error<
-  "statement in 'omp parallel sections' directive must be enclosed into a section region">;
+  "statement in 'omp %0' directive must be enclosed into a section region">;
 def err_omp_parallel_reduction_in_task_firstprivate : Error<
   "argument of a reduction clause of a %0 construct must not appear in a firstprivate clause on a task construct">;
 def err_omp_atomic_read_not_expression_statement : Error<