[llvm] [VPlan] Defer to preservesUniformity in isElementWise (PR #215763)

[via llvm-commits]

github-actions[bot] wrote:

test-suite diff from 11eba5ca3511b1039d5e672b3d886bd5b9fc5807...1d2c1070701d45f4825ec966d65bdd37e4446eaa: https://github.com/llvm/llvm-project/actions/runs/31584248780/artifacts/9139527269

Statistics: https://github.com/llvm/llvm-project/actions/runs/31584248780/artifacts/9139527773

## riscv64-linux-gnu `-march=rva23u64 -O3`
| ('Program', '')                             |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:--------------------------------------------|-------------------------:|-------------------------:|-------------------------:|
| test-suite...lications/SIBsim4/SIBsim4.test |                    27288 |                    27336 |              0.00175901  |
| Geomean difference                          |                      nan |                      nan |              2.09601e-06 |
## aarch64-linux-gnu `-march=armv9-a -O3`
| ('Program', '')                             |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:--------------------------------------------|-------------------------:|-------------------------:|-------------------------:|
| test-suite...lications/SIBsim4/SIBsim4.test |                    37548 |                    37596 |              0.00127836  |
| Geomean difference                          |                      nan |                      nan |              3.96755e-06 |
## x86_64-linux-gnu `-march=x86-64-v3 -O3`
| ('Program', '')    |   ('size..text', 'base') |   ('size..text', 'head') |   ('size..text', 'diff') |
|:-------------------|-------------------------:|-------------------------:|-------------------------:|
| Geomean difference |                      nan |                      nan |               -2.104e-06 |


https://github.com/llvm/llvm-project/pull/215763