Using external PostgreSQL should not require superuser rights

[tolusha]

Is your enhancement related to a problem? Please describe.

This PRs [1] [2] allows to use external DB with Che.
Unfortunately che database user is required superuser rights for instance to create extension [3]
This is might not be acceptable in some cases.

Describe the solution you'd like

Figure out if this extension is needed and if is not then remove its creation.

Describe alternatives you've considered

If extension is still needed

• remove its creation anyway from che-server side
• document as additional requirements for external DB usage
• move its creation to operator for non-external DB case

Additional context

#17274

[1] eclipse-che/che-docs#1430
[2] eclipse-che/che-operator#371
[3] https://github.com/eclipse/che/blob/master/wsmaster/che-core-sql-schema/src/main/resources/che-schema/5.11.0/postgresql/1__optimize_user_search.sql

[che-bot]

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