fix(cmn): update log lines for service shutdown

Improves the log lines within BaseServiceV2 when the service is being
shut down. Follows the pattern already laid out in the main() function
which will log when key events happen.

.changeset/good-knives-add.md

@@ -0,0 +1,5 @@
+---
+'@eth-optimism/common-ts': patch
+---
+
+Update log lines for service shutdown

packages/common-ts/src/base-service/base-service-v2.ts

@@ -207,7 +207,7 @@ export abstract class BaseServiceV2<
 
     // Gracefully handle stop signals.
     const stop = async (signal: string) => {
-      this.logger.info(`stopping service`, { signal })
+      this.logger.info(`stopping service with signal`, { signal })
       await this.stop()
       process.exit(0)
     }
@@ -263,9 +263,11 @@ export abstract class BaseServiceV2<
     this.running = false
 
     // Wait until the main loop has finished.
+    this.logger.info('stopping service, waiting for main loop to finish')
     while (!this.done) {
       await sleep(1000)
     }
+    this.logger.info('main loop finished, goodbye!')
   }
 
   /**