[WebGPU] Fail configure if WebGPU EP source basenames collide
Add a configure-time check that every compiled source in
onnxruntime_providers_webgpu has a unique file name (ignoring directory,
extension and case), so a new same-named file fails fast instead of
reintroducing the MSVC SARIF log collision that the renames remove from this
target. The error lists every colliding pair at once.
The check covers only this target; other ORT targets still have same-named
sources. It runs before the static/plugin source filtering, so
static-library-only builds also reject names that would collide in the plugin
builds. It is a stop-gap that can be removed once the logging gives each
translation unit its own log name.
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>