[Documentation]: Removal of the platforms folder under docs and move all provider info to the providers folder

[sepiatone]

Checked

• I searched existing ideas and did not find a similar one
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• I've clearly described the feature request and motivation for it

Feature request

Background

The platforms folder (under docs\docs) has information on the following providers - Anthropic, AWS, Google, Hugging Face, Microsoft and OpenAI, besides an index page. Information on other providers is in the providers folder (also under docs\docs).

Proposal

Move all provider information from the platforms folder to the provider folder.

Motivation

This change will make the system (slightly) easier to maintain. Now (understandably) there is some confusion as to where to place the documentation (for e.g. see #19521)

This change will be transparent to the end user.

Proposal (If applicable)

Move all provider information from the platforms folder to the provider folder.

[sepiatone]

See discussion in #20256.