fix: create pg_stat_kcache extension before running of an observing session

Description

Create pg_stat_kcache extension before running of an observing session as observing uses the pg_stat_kcache_reset() function

{
  "code": "INTERNAL_ERROR",
  "message": "ERROR: function pg_stat_kcache_reset() does not exist (SQLSTATE 42883)"
}

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Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
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