Cardano Updates

PR review comments

io-sim improvments

Asynchronous exceptions might be coming from outside of a simulation, for
example when using QuickCheck's `within` function.

An exception provided as an argument to `throwIO` or `throwTo`  might be
a bottom value itself.  This is fine in general, since `throwIO` and
`throwTo` are lazy, it's a `catch` handler or the top level handler role
to evaluate them.   `IOSim` supports this, but we need to away to
display trace in presence of bottoms in `EventThrow` and `EventThrowTo`.
We use `unsafePerformIO` to evaluate `show e` to NF before including it
the trace.

With the included patch the trace of
```haskell
sim :: IOSim s ()
sim = throwIO (error "bottom")
```
will contain
```
Throw - error evaluating exception: bottom
```
in `ppTrace` output.

This patch makes `say` behave similar to how `putStrLn` does:
evaluate its argument to `NF` and throw an exception if evaluation
fails. The same applies to the `MonadSay` instance of the `STM (IOSim
s)` monad.

For `traceM` and `traceSTM` we move evaluation from these functions, to
the simulators (IOSim, IOSimPOR), which allows to throw an exception
within the simulator.

Added flushEventLog to MonadEventlog

Asynchronous exceptions might be coming from outside of a simulation, for
example when using QuickCheck's `within` function.

An exception provided as an argument to `throwIO` or `throwTo`  might be
a bottom value itself.  This is fine in general, since `throwIO` and
`throwTo` are lazy, it's a `catch` handler or the top level handler role
to evaluate them.   `IOSim` supports this, but we need to away to
display trace in presence of bottoms in `EventThrow` and `EventThrowTo`.
We use `unsafePerformIO` to evaluate `show e` to NF before including it
the trace.

With the included patch the trace of
```haskell
sim :: IOSim s ()
sim = throwIO (error "bottom")
```
will contain
```
Throw - error evaluating exception: bottom
```
in `ppTrace` output.

This patch makes `say` behave similar to how `putStrLn` does:
evaluate its argument to `NF` and throw an exception if evaluation
fails. The same applies to the `MonadSay` instance of the `STM (IOSim
s)` monad.

For `traceM` and `traceSTM` we move evaluation from these functions, to
the simulators (IOSim, IOSimPOR), which allows to throw an exception
within the simulator.