Simplify/clarify watchdog code

- Use Debug trait object rather than arbitrary closure
- Combine bool+Instant into Option<Instant>
- Disambiguate "timeout"
- Add comments
- Simplify multi-argument matches

Test: keystore2_test
Test: libwatchdog_rs.test
Flag: None, refactor
Change-Id: Ieb16257c763fc2e04d592d97f341fea27aad726f
diff --git a/keystore2/src/service.rs b/keystore2/src/service.rs
index 3726358..b760a56 100644
--- a/keystore2/src/service.rs
+++ b/keystore2/src/service.rs
@@ -381,9 +381,7 @@
         &self,
         security_level: SecurityLevel,
     ) -> binder::Result<Strong<dyn IKeystoreSecurityLevel>> {
-        let _wp = wd::watch_millis_with("IKeystoreService::getSecurityLevel", 500, move || {
-            format!("security_level: {}", security_level.0)
-        });
+        let _wp = wd::watch_millis_with("IKeystoreService::getSecurityLevel", 500, security_level);
         self.get_security_level(security_level).map_err(into_logged_binder)
     }
     fn getKeyEntry(&self, key: &KeyDescriptor) -> binder::Result<KeyEntryResponse> {