Convert entity operation hrefs to route names and parameters

Entity operation links still use href instead of route name and parameters in their definitions for two reasons:

• theme_links() did not support routes until #2102777: Allow theme_links to use routes as well as href was committed two weeks ago.
• URL paths are predictable 80% of the time, while we have no predictable format for route names. In most cases entities' edit paths are identical to their canonical URL paths, but suffixed with /edit, for instance.

This issue depends on #1839516: Introduce entity operation providers for easier fixing.