CI observability enhancements. (#1193)

- Adds a a `--log-root` option to `swift system start`, propagating the
value as `CONTAINER_LOG_ROOT` to services for logging to files instead
of the OS log facility. This is not a "production" capability as it
neither merges nor rotates logs.
- Currently we don't collect logs on CI builds, and we don't have
permission to run the `log` command there. The PR adds `--log-root` to
the CI test phase, archives the results, and uploads the archive as an
artifact.
- Use FilePath from swift-system for the log root. Foundation URL is a
bit of a footgun for filesystem paths, so unless we identify a
showstopper, we should incrementally transition to this type everywhere
except where we really need network URLs.
- Output the hostname of the CI runner at the start of the test phase so
we can identify runner-specific issues where they exist.
- Fix formatting for log messages with multiple metadata items, and fix
unstructured messages on instances that weren't found using `grep -r
'log\.' Sources`.
- Adds command reference documentation for `--log-root`.

Sources/Helpers/Images/ImagesHelper.swift

@@ -54,11 +54,14 @@ extension ImagesHelper {
 
         var installRoot = InstallRoot.url
 
+        var logRoot = LogRoot.path
+
         private static let unpackStrategy = SnapshotStore.defaultUnpackStrategy
 
         func run() async throws {
             let commandName = ImagesHelper._commandName
-            let log = setupLogger()
+            let logPath = logRoot.map { $0.appending("\(commandName).log") }
+            let log = ServiceLogger.bootstrap(category: "ImagesHelper", debug: debug, logPath: logPath)
             log.info("starting helper", metadata: ["name": "\(commandName)"])
             defer {
                 log.info("stopping helper", metadata: ["name": "\(commandName)"])
@@ -77,7 +80,12 @@ extension ImagesHelper {
                 log.info("starting XPC server")
                 try await xpc.listen()
             } catch {
-                log.error("helper failed", metadata: ["name": "\(commandName)", "error": "\(error)"])
+                log.error(
+                    "helper failed",
+                    metadata: [
+                        "name": "\(commandName)",
+                        "error": "\(error)",
+                    ])
                 ImagesHelper.exit(withError: error)
             }
         }
@@ -114,19 +122,5 @@ extension ImagesHelper {
             routes[ImagesServiceXPCRoute.contentIngestCancel.rawValue] = harness.cancelIngestSession
             routes[ImagesServiceXPCRoute.contentIngestComplete.rawValue] = harness.completeIngestSession
         }
-
-        private func setupLogger() -> Logger {
-            LoggingSystem.bootstrap { label in
-                OSLogHandler(
-                    label: label,
-                    category: "ImagesHelper"
-                )
-            }
-            var log = Logger(label: "com.apple.container")
-            if debug {
-                log.logLevel = .debug
-            }
-            return log
-        }
     }
 }