Simplify pageserver initialization & configuration

[VladLazar]

See https://github.com/neondatabase/aws/pull/1322

[VladLazar]

Last week (ending 2024-05-17):

• pageserver pr: pageserver: use identity file as node is authority and remove init command and config-override flags #7766
• cplane pr to remove usage of config override: https://github.com/neondatabase/cloud/pull/13417
• ansible pr: https://github.com/neondatabase/aws/pull/1322

Pageserver and ansible changes are good to go, but cplane usage of --config-override is blocking them.
The cplane changes have to merge first. Once that's done apply the plan from here:
https://www.notion.so/neondatabase/Rollout-Plan-simplified-pageserver-initialization-f935ae02b225444e8a41130b7d34e4ea

Once Christian and/or Vlad are back from holiday:

• Get cplane pr merged (doesn't 100% work in current state)
• Apply rollout plan https://www.notion.so/neondatabase/Rollout-Plan-simplified-pageserver-initialization-f935ae02b225444e8a41130b7d34e4ea