This PR replaces Geth's logger package (a fork of [log15](https://github.com/inconshreveable/log15)) with an implementation using slog, a logging library included as part of the Go standard library as of Go1.21.
Main changes are as follows:
* removes any log handlers that were unused in the Geth codebase.
* Json, logfmt, and terminal formatters are now slog handlers.
* Verbosity level constants are changed to match slog constant values. Internal translation is done to make this opaque to the user and backwards compatible with existing `--verbosity` and `--vmodule` options.
* `--log.backtraceat` and `--log.debug` are removed.
The external-facing API is largely the same as the existing Geth logger. Logger method signatures remain unchanged.
A small semantic difference is that a `Handler` can only be set once per `Logger` and not changed dynamically. This just means that a new logger must be instantiated every time the handler of the root logger is changed.
----
For users of the `go-ethereum/log` module. If you were using this module for your own project, you will need to change the initialization. If you previously did
```golang
log.Root().SetHandler(log.LvlFilterHandler(log.LvlInfo, log.StreamHandler(os.Stderr, log.TerminalFormat(true))))
```
You now instead need to do
```golang
log.SetDefault(log.NewLogger(log.NewTerminalHandlerWithLevel(os.Stderr, log.LevelInfo, true)))
```
See more about reasoning here: https://github.com/ethereum/go-ethereum/issues/28558#issuecomment-1820606613
This change updates our urfave/cli dependency to the v2 branch of the library.
There are some Go API changes in cli v2:
- Flag values can now be accessed using the methods ctx.Bool,
ctx.Int, ctx.String, ... regardless of whether the flag is 'local' or
'global'.
- v2 has built-in support for flag categories. Our home-grown category
system is removed and the categories of flags are assigned as part of
the flag definition.
For users, there is only one observable difference with cli v2: flags must now
strictly appear before regular arguments. For example, the following command is
now invalid:
geth account import mykey.json --password file.txt
Instead, the command must be invoked as follows:
geth account import --password file.txt mykey.json
TAP is a text format for test results. Parsers for it are available in many languages,
making it easy to consume. I want TAP output from our protocol tests because the
Hive wrapper around them needs to know about the test names and their individual
results and logs. It would also be possible to just write this info as JSON, but I don't
want to invent a new format.
This also improves the normal console output for tests (when running without --tap).
It now prints -- RUN lines before any output from the test, and indents the log output
by one space.
