[pidcat] Allow package to specify a process as well …

Add a process name filtering method in addition to package filtering. This means the package argument would now be more of a process name with some specific rules, which is easier to manage than adding a -p argument (annoying to match with multiple arguments).

With this change, `pidcat com.android.chrome' will match all of chrome's processes, 'pidcat com.android.chrome:` will only match its main process and `pidcat com.android.chrome:sandboxed_process1` will match the first sandbox process.

Note that existing users aren't affected since normal package names are still treated as matching all processes as before.