[prism] move test functions and tests to internal_test

[lostluck]

Move prism test functions and tests to internal_test to break ptest dependency cycle.

See #27550 and #24789.

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[codecov]

Codecov Report

Merging #27714 (d679a21) into master (4d712eb) will decrease coverage by 0.04%.
Report is 8 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #27714      +/-   ##
==========================================
- Coverage   70.92%   70.89%   -0.04%     
==========================================
  Files         861      860       -1     
  Lines      104808   104625     -183     
==========================================
- Hits        74340    74177     -163     
+ Misses      28910    28893      -17     
+ Partials     1558     1555       -3     

Flag	Coverage Δ
go	53.37% <ø> (-0.19%)	⬇️

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[lostluck]

This change is smaller than it looks, it's just a move, and changing to use internal_test test package for the dependency break.

[jrmccluskey]

LGTM