cmd/evm, cmd/clef, cmd/bootnode: fix / unify logging (#28696)

This change fixes a problem with our non-core binaries: evm, clef, bootnode.

First of all, they failed to convert from legacy loglevels 1 to 5, to the new slog loglevels -4 to 4.

Secondly, the logging was actually setup in the init phase, and then overridden in the main. This is not needed for evm, since it used the same flag name as the main geth verbosity. Better to let the flags/internal handle the logging init.

cmd/clef/main.go

@@ -57,7 +57,6 @@ import (
 	"github.com/mattn/go-colorable"
 	"github.com/mattn/go-isatty"
 	"github.com/urfave/cli/v2"
-	"golang.org/x/exp/slog"
 )
 
 const legalWarning = `
@@ -493,7 +492,8 @@ func initialize(c *cli.Context) error {
 	if usecolor {
 		output = colorable.NewColorable(logOutput)
 	}
-	log.SetDefault(log.NewLogger(log.NewTerminalHandlerWithLevel(output, slog.Level(c.Int(logLevelFlag.Name)), usecolor)))
+	verbosity := log.FromLegacyLevel(c.Int(logLevelFlag.Name))
+	log.SetDefault(log.NewLogger(log.NewTerminalHandlerWithLevel(output, verbosity, usecolor)))
 
 	return nil
 }