[migrator] Filter out diag::wrong_argument_labels for the fixit pass
The migrator only applies changes from the APIDiffMigratorPass in the primary
file. This means that if a nominal type was renamed, for example, any members
users have added in an extension in a separate file won't be visible, because
the extension would still have the old name. This can result in 'wrong argument
label' errors with fixits to change the argument labels that, when applied by
the fixit pass, completely change which function was being called and cause
post-migration errors.
This patch updates the fixit pass to ignore diag::wrong_argument_labels.
diag::extra_argument_labels and diag::missing_argument_labels were already
filtered out for other reasons.
Resolves rdar://problem/40170377