BackendLoaderTest drives ProbeIndirectInstanceIdIncludesBaseInstance
(now externally linked) against a fake GLES function table: conforming
and ANGLE-style leaking drivers, the no-vertex-SSBO skip, draw-error
inconclusiveness, object cleanup, and the FillInGLESCapabilities wiring
end-to-end. SanityTest gains PromoteDrawParameterGlobalsToUniforms
cases pinning the mg_ZeroBasedInstanceID rewrite and the
last-SSBO-binding computation against a non-default binding count,
with RAII capability restoration.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>