Make it possible to quickly jump to the (per-project - #1517) compilation buffer if there's already one. I mention #1517 because this becomes even more useful with that, as there may be many compilation buffers to select between otherwise.

A complication here is if you have a running projectile-test-project, then you try to use projectile-run-project to switch to it ... they're different commands, so the "raise" might be confusing. Not sure what the right solution is -- maybe have distinct compilation buffers for each "type" of compilation, or maybe check the top of the compilation buffer, if it's not the same command as would be run otherwise, then ask if you want to switch or run the new command?

Expected behavior

C-c p c switches to the compilation buffer if there is one (where I can hit g if it's not running), otherwise it starts a new compilation process in a new buffer

Actual behavior

When there's already a running compilation process, C-c p c says "A compilation process is running; kill it?"

Steps to reproduce the problem

Type C-c p c while a compilation is running.

Environment & Version information

Projectile version information

Projectile 20191216.2105

Emacs version

GNU Emacs 26.3 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.13)

Operating system

NixOS 20.03