[Docs RFC] Update docs to remove CentOS, have correct versions of Postgres support and align supported platforms

[billy-the-fish]

CentOs 7 is no longer supported, the list of Postgres platforms is incorrect and the linux install needs rockylinux install. To fix this:

• Update https://docs.timescale.com/self-hosted/latest/install/installation-linux/ to include RockyLinux and mark ArchLinux as community supported.
• Update https://docs.timescale.com/self-hosted/latest/tooling/install-toolkit/ to remove CentOS and have the same platforms and structure as the install guide.
• Update https://docs.timescale.com/use-timescale/latest/upgrades/#upgrade-to-a-new-postgresql-version to point to a new Supported platforms page.
• Create the new supported platforms page with all the correct versions of everything.
• Remove any mention of product versions from anywhere in the docs, and point to the supported platforms page.