Description: The CPU EP MVN kernel doesn't actually support the axes parameter (any arbitrary axes), which caused some test failures when comparing against the DML EP (which fully supports axes). Not supporting them is okay, but what's worse is that the code silent returns the wrong results for unsupported combinations, like HW and NC, which get mapped blindly and incorrectly to NCHW. This change more robustly checks the axes parameter, rather than just checking for the presence of axis 1 without checking the other axes, given the CPU EP only supports 4D NCHW and NHW.

Motivation and Context

• Why is this change required? What problem does it solve?
• If it fixes an open issue, please link to the issue here. MeanVarianceNormalization v9 CPU kernel doesn't honor axes attribute #1828

onnxruntime_test_all.exe
...
[==========] 3319 tests from 230 test suites ran. (372903 ms total)
[  PASSED  ] 3319 tests.

Given the old logic, wouldn't HW be mapped to NHW and NC would get mapped to NCHW (as opposed to both getting mapped to NCHW) ?

@hariharans29 Correct - fixed PR description (I typed it correctly in my original issue :b).