[migractions] Better handle removal of RQLConstraint in sync_schema
In rdef synchronisation, filter unmodified constraints before processing the
sets of old and new constraints.
Add a new `constraint_by_eid` method on RelationDefinitionSchema, which
eliminates the ambiguity of `constraint_by_type` usage when several
constraints of the same type are involved in the same migration.
Closes #3633644.
msgid ""
msgstr ""
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Generated-By: pygettext.py 1.5\n"
"Plural-Forms: nplurals=2; plural=(n > 1);\n"