Auto merge of #135047 - Flakebi:amdgpu-kernel-cc, r=workingjubilee

Add gpu-kernel calling convention

The amdgpu-kernel calling convention was reverted in commit f6b21e90d1ec01081bc2619efb68af6788a63d65 (#120495 and rust-lang/rust-analyzer#16463) due to inactivity in the amdgpu target.

Introduce a `gpu-kernel` calling convention that translates to `ptx_kernel` or `amdgpu_kernel`, depending on the target that rust compiles for.

Tracking issue: #135467
amdgpu target tracking issue: #135024

Author: bors