Add unit tests for HIST_count_wksp

Add unit tests for HIST_count_wksp

The following tests are included:
- Empty input scenario test.
- Workspace size and alignment tests.
- Symbol out-of-range tests.
- Cover multiple input sizes, vary permitted maximum symbol
  values, and include diverse symbol distributions.

These tests verifies count table correctness, maxSymbolValuePtr
updates, and error-handling paths. It enables automated regression
of core histogram logic as well.