Bump Version for Az.Storage v3.12.1-preview

[BethanyZhou]

Description

Bump Version for Az.Storage v3.12.1-preview

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate ChangeLog.md file(s) has been updated:
  • For any service, the ChangeLog.md file can be found at src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md
  • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header -- no new version header should be added
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • a cmdlet design review was approved for the changes in this repository (Microsoft internal only)
    • {Please put the link here}
  • the markdown help files have been regenerated using the commands listed here

[blueww]

tools/Tools.Common/SerializedCmdlets/Az.Storage.json should not be checked in.
Per my understaning, this file is used to track breaking change of Az.Storage. But we allows breaking in preview module, and don't need to track breaking in preview module.