Add completions: alter role, create/alter/drop policy, comment, analyze, alter function

[rolang]

Support for completions:

• ALTER ROLE
• CREATE POLICY , ALTER POLICY, DROP POLICY
• COMMENT
• ANALYZE
• ALTER FUNCTION

(Re-targeted branch of #1039)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (73f2f36) 85.45% compared to head (553d3d3) 85.50%.

Additional details and impacted files

@@               Coverage Diff                @@
##           series/0.6.x    #1041      +/-   ##
================================================
+ Coverage         85.45%   85.50%   +0.05%     
================================================
  Files               132      132              
  Lines              2008     2015       +7     
  Branches            239      237       -2     
================================================
+ Hits               1716     1723       +7     
  Misses              292      292              

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