Add MigrateDatabase RPC to APIService for database migration

[Warashi]

What this PR does:

as title

Why we need it:

When developing pipedv1, we have to use data with new fields, such as deploy target, or we have to patch pipedv1 temporarily to use the old field.
This PR defines the API to convert the existing data to prepare the data with new fields.

Which issue(s) this PR fixes:

Part of #4980

Does this PR introduce a user-facing change?: No

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.18%. Comparing base (6a0e67e) to head (a94b235).
Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5476      +/-   ##
==========================================
- Coverage   26.19%   26.18%   -0.02%     
==========================================
  Files         458      458              
  Lines       49172    49172              
==========================================
- Hits        12881    12875       -6     
- Misses      35267    35273       +6     
  Partials     1024     1024              

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[ffjlabo]

LGTM