Change v2 mac_android_aot_engine orchestrator builder to Linux (#41181)

`mac_android_aot_engine` orchestrator kicks off Mac swarming tasks, but don't seem to need to run on a Mac.  Swap Linux bots which are more plentiful and have a shorter queue time.

Start by adding new `bringup` builder to see if it passes in staging.  If it passes I will remove the Mac variants ASAP.

Keep `mac_ios_engine` and `mac_host_engine` as Macs since they need to run Xcodes on Macs to create the xcframeworks.

Author: jmagman

.ci.yaml

@@ -346,8 +346,13 @@ targets:
     timeout: 60
     properties:
       config_name: mac_android_aot_engine
-      $flutter/osx_sdk : >-
-        { "sdk_version": "14a5294e" }
+
+  - name: Linux mac_android_aot_engine
+    bringup: true
+    recipe: engine_v2/engine_v2
+    timeout: 60
+    properties:
+      config_name: mac_android_aot_engine
 
   - name: Mac mac_host_engine
     recipe: engine_v2/engine_v2