salt.modules.pip: Installing with the editable option does not validate local path correctly on Windows

Description of Issue

When specifying the editable option, the salt.modules.pip_state module checks the path that is passed in order to determine whether a local or remote path is specified. This is done by checking if the path begins with a "/" which can be incorrect on Windows.

salt.modules.pip.py:849

    if editable:
        egg_match = re.compile(r'(?:#|#.*?&)egg=([^&]*)')
        if isinstance(editable, six.string_types):
            editable = [e.strip() for e in editable.split(',')]

        for entry in editable:
            # Is the editable local?
            if not (entry == '.' or entry.startswith(('file://', '/'))):
                match = egg_match.search(entry)

                if not match or not match.group(1):
                    # Missing #egg=theEggName
                    raise CommandExecutionError(
                        'You must specify an egg for this editable'
                    )
            cmd.extend(['--editable', entry])

When the loop iterates through the list of editable paths, the entry is checked for "file://" and "/" in order to validate whether the editable is local or not. On windows, paths can begin with a letter followed by a ":".

Here's a regex that can probably be used to test for a valid windows path: ^[a-zA-Z]:\\[\\\S|*\S]?.*$. This appears exhaustive, but should probably be verified.

Setup

Install a salt-minion on windows.

Steps to Reproduce Issue

C> salt-call --local pip.install editable=C:/local-file-path`
Error running 'pip.install': You must specify an egg for this editable

Versions Report

Although the version here is 2019.2.0, it's in all versions as prior mentioned since commit 0bd2f6c06ee5196cde89271cc4752238539a29c9.

Salt Version:
           Salt: 2019.2.0
 
Dependency Versions:
           cffi: 1.11.5
       cherrypy: 17.4.1
       dateutil: 2.7.5
      docker-py: Not Installed
          gitdb: 2.0.5
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.10
        libgit2: Not Installed
        libnacl: 1.6.1
       M2Crypto: Not Installed
           Mako: 1.0.7
   msgpack-pure: Not Installed
 msgpack-python: 0.6.2
   mysql-python: Not Installed
      pycparser: 2.19
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.15 (v2.7.15:ca079a3ea3, Apr 30 2018, 16:22:17) [MSC v.1500 32 bit (Intel)]
   python-gnupg: 0.4.3
         PyYAML: 3.13
          PyZMQ: 17.1.2
           RAET: Not Installed
          smmap: 2.0.5
        timelib: 0.2.4
        Tornado: 5.1.1
            ZMQ: 4.2.5
 
System Versions:
           dist:   
         locale: cp1252
        machine: AMD64
        release: 8
         system: Windows
        version: 8 6.2.9200 SP0 Multiprocessor Free

Start by reading salt.modules.pip.py around line 849 and reproduce the reported salt-call command on Windows. Update the editable-path validation so a local Windows path such as C:/local-file-path is accepted without an egg, while remote editables still require one; verify the reported error no longer occurs.