feat: add config processor mapping parsed config to NatsOptions

Port of Go server/opts.go processConfigFileLine switch. Maps parsed
NATS config dictionaries to NatsOptions fields including:
- Core options (port, host, server_name, limits, ping, write_deadline)
- Logging (debug, trace, logfile, log rotation)
- Authorization (single user, users array with permissions)
- TLS (cert/key/ca, verify, pinned_certs, handshake_first)
- Monitoring (http_port, https_port, http/https listen, base_path)
- Lifecycle (lame_duck_duration/grace_period)
- Server tags, file paths, system account options

Includes error collection (not fail-fast), duration parsing (ms/s/m/h
strings and numeric seconds), host:port listen parsing, and 56 tests
covering all config sections plus validation edge cases.

tests/NATS.Server.Tests/TestData/auth.conf

@@ -0,0 +1,11 @@
+authorization {
+  user: admin
+  password: "s3cret"
+  timeout: 5
+
+  users = [
+    { user: alice, password: "pw1", permissions: { publish: { allow: ["foo.>"] }, subscribe: { allow: [">"] } } }
+    { user: bob, password: "pw2" }
+  ]
+}
+no_auth_user: "guest"