Factor out usages of child_process spawning

[zepumph]

In the last month or two, many more copies of spawn() have been hard coded into our processes. This is because execute is unwieldy and heavy weight, and it too scary to change. At this time we have 8 copies of spawn in chipper and perennial. Let's also look at exec and execSync is we are so inclined.

[samreid]

In my opinion, execute is problematic and should be avoided:

    // {'reject'|'resolve'} - whether errors should be rejected or resolved.  If errors are resolved, then an object
    //                      - of the form {code:number,stdout:string,stderr:string} is returned. 'resolve' allows usage
    //                      - in Promise.all without exiting on the 1st failure

It sounds like we were unaware of Promise.allSettled.

childProcessShell: cmd !== 'node' && cmd !== 'git' && /^win/.test( process.platform )

This option is never exercised.

      stderr += data;
      grunt.log.debug( `stderr: ${data}` );
      winston.debug( `stderr: ${data}` );

Why do we have 3 channels for the stderr?

Why have an option that radically changes the behavior? Is ExecuteError valuable?

In my opinion, it is clearer and more idiomatic to use spawn directly. We should learn to use it and become comfortable with it. The main/only thing we should factor out to spawn usages is shell: /^win/.test( process.platform )