Switch to log/slog

This change switches GARM to the new structured logging standard
library. This will allow us to set log levels and reduce some of
the log spam.

Given that we introduced new knobs to tweak logging, the number of
config options for logging now warrants it's own section.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

testdata/config.toml

@@ -35,15 +35,36 @@ webhook_url = "https://garm.example.com/webhooks"
 # webhooks for repositories or organizations.
 enable_webhook_management = true
 
+# DEPRECATED: Use the [logging] section to set this option.
 # Uncomment this line if you'd like to log to a file instead of standard output.
 # log_file = "/tmp/runner-manager.log"
 
+# DEPRECATED: Use the [logging] section to set this option.
 # Enable streaming logs via web sockets. Use garm-cli debug-log.
 enable_log_streamer = false
 
 # Enable the golang debug server. See the documentation in the "doc" folder for more information.
 debug_server = false
 
+
+[logging]
+# Uncomment this line if you'd like to log to a file instead of standard output.
+# log_file = "/tmp/runner-manager.log"
+
+# enable_log_streamer enables streaming the logs over websockets
+enable_log_streamer = true
+# log_format is the output format of the logs. GARM uses structured logging and can
+# output as "text" or "json"
+log_format = "text"
+# log_level is the logging level GARM will output. Available log levels are:
+#  * debug
+#  * info
+#  * warn
+#  * error
+log_level = "debug"
+# log_source will output information about the function that generated the log line.
+log_source = false
+
 [metrics]
 # Toggle metrics. If set to false, the API endpoint for metrics collection will
 # be disabled.