Preparing general docs for GA release

[Andriciuc]

Updated the introduction with the proper extension name, updated the intro to reflect this. Removed important note about not meant for production and added the No upgrade warning from previous versions (like RC2) to GA. Updates:

• removed the block announcement for RC2 at the top of the HTML page in the intro
• Added the warning note before installation begins too.
• Updated site name to full name.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-17.5.2@f631496). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release-17.5.2     #434   +/-   ##
=================================================
  Coverage                  ?   84.67%           
=================================================
  Files                     ?       21           
  Lines                     ?     2591           
  Branches                  ?      402           
=================================================
  Hits                      ?     2194           
  Misses                    ?      316           
  Partials                  ?       81           

Components	Coverage Δ
access	81.11% <0.00%> (?)
catalog	88.22% <0.00%> (?)
common	77.77% <0.00%> (?)
encryption	73.45% <0.00%> (?)
keyring	72.88% <0.00%> (?)
src	91.48% <0.00%> (?)
smgr	94.88% <0.00%> (?)
transam	∅ <0.00%> (?)

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