DOC: Clarify requirements for running on GPU and supported configurations

[david-cortes-intel]

Description

Add a comprehensive description of proposed changes

List associated issue number(s) if exist(s): #6 (for example)

Documentation PR (if needed): #1340 (for example)

Benchmarks PR (if needed): IntelPython/scikit-learn_bench#155 (for example)

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This PR:

• Updates the information about which configurations are supported on each distribution channel (latest conda release has DPC and SPMD modules).
• Updates the list of supported python and sklearn versions to reflect the current situation in the main branch.
• Updates the description of GPU support logic.
• Updates the requirements on GPU software that is needed.
• Improves the examples by adding direct links to DPCTL docs, more code snippets, fixing typos, etc.

Checklist to comply with before moving PR from draft:

PR completeness and readability

• I have reviewed my changes thoroughly before submitting this pull request.
• I have updated the documentation to reflect the changes or created a separate PR with update and provided its number in the description, if necessary.
• Git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details).
• I have added a respective label(s) to PR if I have a permission for that.
• I have resolved any merge conflicts that might occur with the base branch.

Testing

• I have run it locally and tested the changes extensively.

Performance

Not applicable.

[codecov]

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