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

@@ -24,7 +24,6 @@ typechecker:
     - nox --session typecheck
 
 .testsuite-base:
-  extends: .nox-base
   stage: "Tests"
   needs: []
   coverage: '/TOTAL.*\s+(\d+%)$/'
@@ -40,6 +39,7 @@ typechecker:
 
 "testsuite-py3.10+cuda":
   extends: .testsuite-base
+  image: i10git.cs.fau.de:5005/pycodegen/pycodegen/nox:ubuntu24.04-cuda12.6
   script:
     - nox --session testsuite-3.10
   tags:
@@ -48,6 +48,7 @@ typechecker:
 
 "testsuite-py3.13":
   extends: .testsuite-base
+  image: i10git.cs.fau.de:5005/pycodegen/pycodegen/nox:alpine
   script:
     - nox --session testsuite-3.13