This change
- Removes interface `log.Format`,
- Removes method `log.FormatFunc`,
- unexports `TerminalHandler.TerminalFormat` formatting methods (renamed to `TerminalHandler.format`)
- removes the notion of `log.Lazy` values
The lazy handler was useful in the old log package, since it
could defer the evaluation of costly attributes until later in the
log pipeline: thus, if the logging was done at 'Trace', we could
skip evaluation if logging only was set to 'Info'.
With the move to slog, this way of deferring evaluation is no longer
needed, since slog introduced 'Enabled': the caller can thus do
the evaluate-or-not decision at the callsite, which is much more
straight-forward than dealing with lazy reflect-based evaluation.
Also, lazy evaluation would not work with 'native' slog, as in, these
two statements would be evaluated differently:
```golang
log.Info("foo", "my lazy", lazyObj)
slog.Info("foo", "my lazy", lazyObj)
```
The p2p msgrate tracker is a thing which tries to estimate some mean round-trip times. However, it did so in a very curious way: if a node had 200 peers, it would sort their 200 respective rtt estimates, and then it would pick item number 2 as the mean. So effectively taking third fastest and calling it mean. This probably works "ok" when the number of peers are low (there are other factors too, such as ttlScaling which takes some of the edge off this) -- however when the number of peers is high, it becomes very skewed.
This PR instead bases the 'mean' on the square root of the length of the list. Still pretty harsh, but a bit more lenient.
This change extracts the peer QoS tracking logic from eth/downloader, moving
it into the new package p2p/msgrate. The job of msgrate.Tracker is determining
suitable timeout values and request sizes per peer.
The snap sync scheduler now uses msgrate.Tracker instead of the hard-coded 15s
timeout. This should make the sync work better on network links with high latency.
