Implementing `Drop` for DOM types is being forbidden. This moves the
resource cleanup logic for `GPUShaderModule`, `GPUTexture`, and
`GPUTextureView` to separate helper structs and removes the
`allowDropImpl` flag from the bindings configuration.
Testing: WebGpu tests just cover their cases
Fixes: Partially #26488
Signed-off-by: Domenico Rizzo <domenico.rizzo@gmail.com>