"grep: invalid option -- P" when running start.sh on Mac

I was working through this repo's example on a Mac. When I got to this step...

> Use the start script for starting a ledger & the java application:

...I tried running `./start.sh examples.pingpong.grpc.PingPongGrpcMain` and received this error message...

```
grep: invalid option -- P
usage: grep [-abcdDEFGHhIiJLlMmnOopqRSsUVvwXxZz] [-A num] [-B num] [-C[num]]
[-e pattern] [-f file] [--binary-files=value] [--color=when]
[--context[=num]] [--directories=action] [--label] [--line-buffered]
[--null] [pattern] [file ...]
```

Googling suggests that some (but not all) versions of `grep` include flags `-P, --perl-regexp`

I suppose the regular expressions in `start.sh` should be converted from a Perl regex to a basic regex.

Start by reading start.sh and locate the grep expressions used when running ./start.sh examples.pingpong.grpc.PingPongGrpcMain. Run that command on macOS to reproduce the invalid -P error, then verify the script starts successfully without relying on unsupported grep options.

Written by the indexing model from the issue text.