Register and execute compensations

[slinkydeveloper]

Fix #95

This PR prototypes compensations, that is a way to register closures to be executed in case of a failure. Some properties:

• Compensations are executed only when the thrown error is terminal (thus only when we're going to write out a OutputStreamEntry).
• Compensations are run in the same context/thread of the handler, similarly to sideEffect closures. This simplifies the threading model for the user.
• Only non-completable journal entries are allowed within compensations, that is side effect, clear/set state, complete awakeable, one way calls.
• Compensations are executed in the reverse order used to set them

Example:

// Register the compensation
ctx.compensate(() -> ctx.set(StateKey.of("message", TypeTag.STRING_UTF8), "none"));
// Do some operation
GreetingResponse greetingResponse = ctx.call(GreeterGrpc.getGreetMethod(), greetingRequest("Francesco")).await();
// If the call fails, the compensation above will be executed

[github-actions]

Unit Test Results

275 tests  +14   275 ✔️ +14   13s ⏱️ -1s
  28 suites +  2       0 💤 ±  0 
  28 files   +  2       0 ❌ ±  0 

Results for commit 15dffa6. ± Comparison against base commit 8223cd6.