feat: integrate mprocs

[safwansamsudeen]

Adds two configuration options to bench init:

• --use-mprocs: allows people to use mprocs instead of of honcho - though both are still supported even with this option
• --default-app TEXT: allows developers to set a default app to run the frontend server for

bench start will now use mprocs if mprocs.yaml exists - otherwise it'll use honcho (current working).

Also, if default-app is specified, both use_mprocs and install-app are assumed so that this:

bench init --use-mprocs --install-app drive --default-app drive PATH

becomes:

bench init --default-app drive PATH

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[akhilnarang]

While its fine overall, "default app" sounds weird. Maybe can tweak that flag name.

Also I've noticed many of the apps READMEs had mentioned using yarn, here npm is hardcoded.

I'd prefer adding in some parameter which basically lets you specify a service name + command, and that would get added to procfile/mprocs yaml as chosen.