Upgrade version to 1.2.0 for next release

[VachaShah]

Description

Upgrade version to 1.2.0

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has documentation added
• Commits are signed as per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

Merging #88 (9e0af20) into main (c53ff19) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #88   +/-   ##
=======================================
  Coverage   64.60%   64.60%           
=======================================
  Files          32       32           
  Lines        2328     2328           
=======================================
  Hits         1504     1504           
  Misses        716      716           
  Partials      108      108           

Flag	Coverage Δ
opensearch-cli	64.60% <ø> (ø)

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Files	Coverage Δ
commands/root.go	80.88% <ø> (ø)