fs: Remove github.com/sirupsen/logrus and replace with log/slog

This removes logrus which is not developed any more and replaces it
with the new log/slog from the Go standard library.

It implements its own slog Handler which is backwards compatible with
all of rclone's previous logging modes.

go.mod

@@ -66,7 +66,6 @@ require (
 	github.com/rivo/uniseg v0.4.7
 	github.com/rogpeppe/go-internal v1.14.1
 	github.com/shirou/gopsutil/v4 v4.25.1
-	github.com/sirupsen/logrus v1.9.3
 	github.com/skratchdot/open-golang v0.0.0-20200116055534-eef842397966
 	github.com/spf13/cobra v1.9.1
 	github.com/spf13/pflag v1.0.6
@@ -208,6 +207,7 @@ require (
 	github.com/sabhiram/go-gitignore v0.0.0-20210923224102-525f6e181f06 // indirect
 	github.com/samber/lo v1.47.0 // indirect
 	github.com/shabbyrobe/gocovmerge v0.0.0-20230507112040-c3350d9342df // indirect
+	github.com/sirupsen/logrus v1.9.3 // indirect
 	github.com/sony/gobreaker v0.5.0 // indirect
 	github.com/spacemonkeygo/monkit/v3 v3.0.22 // indirect
 	github.com/tklauser/go-sysconf v0.3.13 // indirect