fix: Support all logger level case variants

#4047 updated
parsing the logger level filter. It removed all case variants outside
fully uppercase (e.g. `INFO`) and the 1st character being upper case
(e.g. `Info`) this removed support for other previously supported
variants e.g. `info`. This commit re-introduces this support such that
all variants should again be supported.

Signed-off-by: Jonathan Woollett-Light <jcawl@amazon.co.uk>

Author: Jonathan Woollett-Light

src/vmm/src/logger/logging.rs

@@ -242,13 +242,13 @@ pub struct LevelFilterFromStrError(String);
 impl FromStr for LevelFilter {
     type Err = LevelFilterFromStrError;
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "Off" | "OFF" => Ok(Self::Off),
-            "Trace" | "TRACE" => Ok(Self::Trace),
-            "Debug" | "DEBUG" => Ok(Self::Debug),
-            "Info" | "INFO" => Ok(Self::Info),
-            "Warn" | "WARN" | "Warning" | "WARNING" => Ok(Self::Warn),
-            "Error" | "ERROR" => Ok(Self::Error),
+        match s.to_ascii_lowercase() {
+            "off" => Ok(Self::Off),
+            "trace" => Ok(Self::Trace),
+            "debug" => Ok(Self::Debug),
+            "info" => Ok(Self::Info),
+            "warn" | "warning" => Ok(Self::Warn),
+            "error" => Ok(Self::Error),
             _ => Err(LevelFilterFromStrError(String::from(s))),
         }
     }