getProcessPlugins() normalises the process array twice

Problem/Motivation

If Migration::getProcessPlugins() is called with no parameter, it does this:

    if (!isset($process)) {
      $process = $this->getProcess();
    }

Migration::getProcess() calls getProcessNormalized(), so $process is now a normalised array.

However, getProcessPlugins() then does this:

      foreach ($this->getProcessNormalized($process) as $property => $configurations) {

This means that getProcessNormalized() has been needlessly called a second time.

Steps to reproduce

Proposed resolution

Only call getProcessNormalized() if $process was passed in.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet