Prepare docs for sub-packages

[leofang]

Close #94. Close #95.

This PR prepares for the documentation infrastructure for adding sub-packages. This introduces a (hopefully one-time only) breaking change to the existing doc urls. Two major changes are:

• cuda-python becomes a landing page for sub-packages (to prepare for RFC: Turn cuda-python into a metapackage #105)
• subdirectories are used for sub-packages' docs
• multi-version doc support is added

Old urls:

• https://nvidia.github.io/cuda-python/
  • https://nvidia.github.io/cuda-python/overview.html
  • https://nvidia.github.io/cuda-python/install.html
  • https://nvidia.github.io/cuda-python/release.html
  • ...

New urls:

• https://nvidia.github.io/cuda-python/
  • will redirects to https://nvidia.github.io/cuda-python/latest/
    • which will be a copy of https://nvidia.github.io/cuda-python/12.6.1/ as of today
  • https://nvidia.github.io/cuda-python/latest/release.html
  • ...
  • https://nvidia.github.io/cuda-python/12.6.1/release.html
  • ...
• https://nvidia.github.io/cuda-python/cuda-bindings
  • will redirects to https://nvidia.github.io/cuda-python/cuda-bindings/latest/
    • which will be a copy of https://nvidia.github.io/cuda-python/cuda-bindings/12.6.1/ as of today
  • https://nvidia.github.io/cuda-python/cuda-bindings/latest/overview.html
  • https://nvidia.github.io/cuda-python/cuda-bindings/latest/install.html
  • https://nvidia.github.io/cuda-python/cuda-bindings/latest/release.html
  • ...
  • https://nvidia.github.io/cuda-python/cuda-bindings/12.6.1/overview.html
  • https://nvidia.github.io/cuda-python/cuda-bindings/12.6.1/install.html
  • https://nvidia.github.io/cuda-python/cuda-bindings/12.6.1/release.html
  • ...
• https://nvidia.github.io/cuda-python/cuda-core
  • will redirects to https://nvidia.github.io/cuda-python/cuda-core/latest/
    • which will be a copy of https://nvidia.github.io/cuda-python/cuda-core/0.1.0/ as of today
  • https://nvidia.github.io/cuda-python/cuda-core/latest/install.html
  • https://nvidia.github.io/cuda-python/cuda-core/latest/release.html
  • ...
  • https://nvidia.github.io/cuda-python/cuda-core/0.1.0/install.html
  • https://nvidia.github.io/cuda-python/cuda-core/0.1.0/release.html
  • ...

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.

[leofang]

This should be ready for review. However, do not merge yet, as I need to do a live demo first before we commit to the changes.

[leofang]

(Updated the PR description to compare the old/existing urls with the new/expected urls.)

[vzhurba01]

LGTM