Update tt configuration and env description to 2.0

[p7nov]

Resolves #3997 #3998 #3836

Deployment: https://docs.d.tarantool.io/en/doc/gh-3997-tt-2-0-cfg/reference/tooling/tt_cli/configuration/

Updated the general tt docs to version 2.0:

• Updated the tt configuration page to 2.0 version:
  • Added the env section and moved tt environment parameters from app to it.
  • Added the info about the new layout of app files: they are created inside instances.enabled/<app-name>/.
  • Removed log rotation parameters.
  • Added migration instructions from tt 1.* to tt 2.*
• Added a note about global options positioning before commands.
• Updated tt logrotate reference to the new behavior.
• Updated log rotation instructions in the admin guide to the new tt logrotate behavior.

To cherry-pick to 2.11

[psergee]

Thank you for the patch. Lgtm.

[xuniq]

LGTM.