Extend Support for CUDA and HIP kernel invocations

This MR extends the support for CUDA and HIP kernel invocations and API reflection in pystencils-sfg, reflecting the concepts introduced in pystencils!449 (merged).

• Move GPU-related stuff into new composer mix-in SfgGpuComposer
• Replace cuda_invoke() by gpu_invoke()
• Implement three separate signatures of gpu_invoke(), depending on the kernel indexing scheme selected by the user
• Replace extensions.gpu by lang.gpu
• Add explanations on GPU kernels to user manual
• Fix some errors and clarify some interface descriptions in the user manual

This MR will already be using Target.HIP and therefore will have to wait for pystencils!458 (merged).

.gitlab-ci.yml

@@ -4,20 +4,20 @@ stages:
   - "Documentation"
   - deploy
 
-.qa-base:
+.nox-base:
   image: i10git.cs.fau.de:5005/pycodegen/pycodegen/nox:alpine
   tags:
     - docker
 
 linter:
-  extends: .qa-base
+  extends: .nox-base
   stage: "Code Quality"
   needs: []
   script:
     - nox --session lint
 
 typechecker:
-  extends: .qa-base
+  extends: .nox-base
   stage: "Code Quality"
   needs: []
   script: