chore: reorganize Prisma CLI reference

[ruheni]

Closes #4697

This PR:

• Moves https://www.prisma.io/docs/concepts/components/prisma-cli/installation to the Reference
• Updates the Reference with an installation step at the top (from components/prisma-cli/installation)
• Adds section at the bottom on CLI usage with an http proxy (from components/prisma-cli/installation)

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 27, 2023 5:38pm

[github-actions]

This PR changes the following pages (Vercel Preview Deploy links):

Changed Vercel links

• /docs/concepts/components/prisma-client/working-with-prismaclient/generating-prisma-client (currently)
• /docs/concepts/components/prisma-client (currently)
• /docs/concepts/components/prisma-migrate/legacy-migrate (currently)
• /docs/concepts/components/prisma-cli (currently)
• /docs/concepts/components/prisma-cli/installation (currently)
• /docs/guides/upgrade-guides/upgrade-from-prisma-1/upgrading-the-prisma-layer (currently)
• /docs/guides/migrate-to-prisma/migrate-from-typeorm (currently)
• /docs/guides/migrate-to-prisma/migrate-from-sequelize (currently)
• /docs/guides/migrate-to-prisma/migrate-from-mongoose (currently)
• /docs/reference/api-reference/command-reference (currently)
• /docs/reference/api-reference/environment-variables-reference (currently)
• /docs/data-platform/data-proxy/prisma-cli-with-data-proxy (currently)

(Note that links will only be valid after Vercel preview deploy succeeded)

[github-actions]

This PR probably requires the following redirects to be added to vercel.json:

  {
    "source": "/docs/concepts/components/prisma-cli/installation",
    "destination": "/docs/##( TODO: Path of page that replaces deleted page )##"
  },

[nikolasburk]

left a few small comments but generally this looks great!