feat(MigrateDumpCommand): Trim underscores from foreign-key constrain…

[paulrrogers]

…t names and reorder them for consistency to workaround PTOSC quirk.

Percona's Online Schema Change can leave behind underscores on constraint names like:

  ...,
  CONSTRAINT _b_fk FOREIGN KEY('b') REFERENCES b ON('b'),
  CONSTRAINT a_fk FOREIGN KEY('a') REFERENCES a ON('a')
);

This enhancement optionally trims those and sorts the constraints as if PTOSC had not been used. This minimizes noise in source control as usage of PTOSC may not be ubiquitous or consistent in all environments, yet the schema is functionally identical.

  ...,
  CONSTRAINT a_fk FOREIGN KEY('a') REFERENCES a ON('a'),
  CONSTRAINT b_fk FOREIGN KEY('b') REFERENCES b ON('b')
);