Runtime init reload after panic

Some runtimes crash with panics because they assume the environment will self recover, because that's Lambda's behavior when you deploy a function. It'd be very useful if the emulator would initialize the runtime again if the runtime crashed with a panic.

Otherwise, people have to restart the emulator, and it's not very obvious that you have to do that by looking at the logs either.

Start by locating the emulator's runtime initialization and panic-handling paths, then trace how a crashed runtime is reported in logs. Done means a panic causes the runtime to initialize again without requiring an emulator restart, with the behavior covered by the relevant tests.

Written by the indexing model from the issue text.