Isn't `set_immediates` failing to validate the `values_offset` it gets from `RenderBundleEncoder::finish`?

[ErichDonGubler]

Isn't set_immediates failing to validate the values_offset it gets from RenderBundleEncoder::finish?

• Those commands arrive in wgpu_core when they're passed to Global::render_bundle_encoder_finish.
• Then RenderBundleEncoder::finish passes them to set_immediates, which places values_offset in an ArcRenderCommand::SetImmediate.
• That will be consumed by RenderBundle::execute here.
• Then this addition may overflow.

Granted, in the end it's just a panic, because the subslicing operation will catch it, but wgpu_core should give an error.

Originally posted by @jimblandy in #9205 (review)

[andyleiserson]

Dynamic offsets and string data are also worth reviewing for similar issues. (I found out-of-bounds issues with those and immediates when I was fuzzing, but at the time I didn't identify a way to reach it from the API, it was only reachable because the fuzzer was writing traces directly.)