Improve Darwin OTA tests.

* Make it possible to hook all the delegate callbacks in the test.
* Add a test for responding BUSY and then being able to handle the retry,
  disabled for now until we make it possible for it to run quickly.

.github/workflows/darwin.yaml

@@ -139,9 +139,12 @@ jobs:
               run: |
                   mkdir -p /tmp/darwin/framework-tests
                   ../../../out/debug/chip-all-clusters-app --interface-id -1 > >(tee /tmp/darwin/framework-tests/all-cluster-app.log) 2> >(tee /tmp/darwin/framework-tests/all-cluster-app-err.log >&2) &
-                  # Make sure ota-requestor is using a different port, discriminator, and KVS from all-clusters-app.
-                  # And a different one from the test harness too; the test harness uses port 5541.
-                  ../../../out/debug/chip-ota-requestor-app --interface-id -1 --secured-device-port 5542 --discriminator 1111 --KVS /tmp/chip-ota-requestor-kvs > >(tee /tmp/darwin/framework-tests/ota-requestor-app.log) 2> >(tee /tmp/darwin/framework-tests/ota-requestor-app-err.log >&2) &
+                  # Make each ota-requestor is using a different port, discriminator, and KVS from
+                  # all-clusters-app and from other requestors.
+                  #
+                  # And a different port from the test harness too; the test harness uses port 5541.
+                  ../../../out/debug/chip-ota-requestor-app --interface-id -1 --secured-device-port 5542 --discriminator 1111 --KVS /tmp/chip-ota-requestor-kvs1 > >(tee /tmp/darwin/framework-tests/ota-requestor-app-1.log) 2> >(tee /tmp/darwin/framework-tests/ota-requestor-app-err-1.log >&2) &
+                  ../../../out/debug/chip-ota-requestor-app --interface-id -1 --secured-device-port 5543 --discriminator 1112 --KVS /tmp/chip-ota-requestor-kvs2 > >(tee /tmp/darwin/framework-tests/ota-requestor-app-2.log) 2> >(tee /tmp/darwin/framework-tests/ota-requestor-app-err-2.log >&2) &
                   xcodebuild test -target "Matter" -scheme "Matter Framework Tests" -sdk macosx OTHER_CFLAGS='${inherited} -Werror -Wconversion -Wno-incomplete-umbrella -Wno-unguarded-availability-new' > >(tee /tmp/darwin/framework-tests/darwin-tests.log) 2> >(tee /tmp/darwin/framework-tests/darwin-tests-err.log >&2)
               working-directory: src/darwin/Framework
             - name: Uploading log files