Implement Retry functionality

[iRevive]

The PR is influenced by #3135.

In my opinion, Retry must carry the error type. That way, we can implement retry functionality on top of the Handle from the cats-mtl.

I also decided to keep the name (perhaps the 'description' fits better?) around. That way, toString provides enough details to understand the retry strategy:

val policy = Retry
  .exponentialBackoff[IO, Throwable](1.second)
  .withCappedDelay(2.seconds)
  .withMaxRetries(10)
  
println(policy)
// MaxRetries(CapDelay(Backoff(baseDelay=1 second, multiplier=Const(2.0), randomizationFactor=0.5), cap=2 seconds), max=5)

---

Usage

Retry on all errors

val policy = Retry
  .exponentialBackoff[IO, Throwable](1.second)
  .withMaxRetries(10)

// retries 10 times at most using an exponential backoff strategy
IO.raiseError(new RuntimeException("oops")).retry(policy)

Retry on some errors (e.g. TimeoutException)

val policy = Retry
  .exponentialBackoff[IO, Throwable](1.second)
  .withMaxRetries(10)
  .withErrorMatcher(Retry.ErrorMatcher[IO, Throwable].only[TimeoutException])

// retries 10 times at most using an exponential backoff strategy
IO.raiseError(new TimeoutException("timeout")).retry(policy)

// gives up immediately
IO.raiseError(new RuntimeException("oops")).retry(policy)

Retry on all errors except the TimeoutException

val policy = Retry
  .exponentialBackoff[IO, Throwable](1.second)
  .withMaxRetries(10)
  .withErrorMatcher(Retry.ErrorMatcher[IO, Throwable].except[TimeoutException])

// retries 10 times at most using an exponential backoff strategy
IO.raiseError(new RuntimeException("oops")).retry(policy)

// gives up immediately
IO.raiseError(new TimeoutException("timeout")).retry(policy)

---

A few points to discuss:

1. A confusion between withMaxDelay, withCappedDelay, withMaxCumulativeDelay. Even though I provided the documentation with examples, these three methods are confusing. Can we find better names?
2. Is my implementation of the exponential backoff correct?

[iRevive]

The evaluation of the retry strategy.

[iRevive]

Retry works with MTL too.

[TobiasRoland]

I'd really love for this to land 🚀 - but I see there's been no comments for 4 months - @iRevive is this waiting on feedback or approvals, or is discussion ongoing somewhere off Github?

[iRevive]

I'd really love for this to land 🚀 - but I see there's been no comments for 4 months - @iRevive is this waiting on feedback or approvals, or is discussion ongoing somewhere off Github?

I'm still waiting for the feedback.