The "update" checkbox should not force update of dependencies

Problem/Motivation

On the migration execute UI page, the checkbox "update" also means that all dependencies will be updated.
This is quite annoying, especially if a dependency migration takes much longer than the actual migration.

Steps to reproduce

Create migrations with inter-dependencies.
Run the dependency migration completely.
Visit a dependent migration "Execute" page.

Check "update" and set limit = 1 (or leave the limit untouched).
Execute.

Expected behavior:
Only one row of the dependent migration is migrated.

Actual behavior:
First the complete dependency migration is imported.
Then the one row from the dependent migration is migrated.
(and all of the dependent migration is marked for update for next run, I believe)

Proposed resolution

Provide separate options for "update" and "update dependencies".

Remaining tasks

User interface changes

API changes

Data model changes