[IA] Create a Platforms section, add FaaS & Kubernetes, etc

[chalin]

Originally posted by @svrnm in #6136

We talked about this during the SIG call yesterday, and it seems that the "Platforms"-idea is what we want to implement, i.e. we create "Platforms" as a new top level category, and it will contain:

• Android
• Browser
• Kubernetes
• FaaS
• Other

This is similar to the grpc-page as @chalin linked to it, and seems to be commonly understood.

@open-telemetry/operator-approvers @open-telemetry/lambda-extension-approvers @open-telemetry/android-approvers @open-telemetry/sandbox-web-js-maintainers @open-telemetry/javascript-approvers PTAL!

Sections to be moved and/or reworked

• FaaS
• Kubernetes
• ...

Tasks

• [IA] New platforms section with Android placeholder, and more #6223
  • [IA] Delete stray page copy already now in platforms #6248
• [IA] Link normalization step for platforms #6232
  • [IA] Revert inadvertent redirects path change #6233
• ...