{POSTGRES} Split postgres flexible server commands from RDBMS

[nasc17]

Related command
az postgres flexible-server

Description
Split postgres flexible-server related commands to its own folder within the module. This would allow from better maintenance of the module from our team.

Similar steps followed by MySQL team: #26531

Testing Guide

History Notes

[Component Name 1] BREAKING CHANGE: az command a: Make some customer-facing breaking change
[Component Name 2] az command b: Add some customer-facing feature

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[azure-client-tools-bot-prd]

Validation for Azure CLI Full Test Starting...

Thanks for your contribution!

[azure-client-tools-bot-prd]

Hi @nasc17,
Since the current milestone time is less than 7 days, this pr will be reviewed in the next milestone.

[azure-client-tools-bot-prd]

Validation for Breaking Change Starting...

Thanks for your contribution!

[yonzhan]

Thank you for your contribution! We will review the pull request and get back to you soon.

[github-actions]

The git hooks are available for azure-cli and azure-cli-extensions repos. They could help you run required checks before creating the PR.

Please sync the latest code with latest dev branch (for azure-cli) or main branch (for azure-cli-extensions).
After that please run the following commands to enable git hooks:

pip install azdev --upgrade
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