[7.17][BK] Migrate ES Forward's agent targeting rules (elastic#187341)

## Summary
The ES forward testing only happens from the direction of 7.17, so this
file only exists on 7.17, thus it's not a backport, but a direct
adjustment of these rules.

Follows up: elastic#184018

.buildkite/pipelines/es_forward.yml

@@ -3,14 +3,20 @@ steps:
     label: Pre-Build
     timeout_in_minutes: 10
     agents:
-      queue: kibana-default
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      machineType: n2-standard-2
 
   - wait
 
   - command: .buildkite/scripts/steps/build_kibana.sh
     label: Build Kibana Distribution and Plugins
     agents:
-      queue: c2-16
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      machineType: c2-standard-16
     key: build
     if: "build.env('KIBANA_BUILD_ID') == null || build.env('KIBANA_BUILD_ID') == ''"
     timeout_in_minutes: 60
@@ -19,7 +25,12 @@ steps:
     label: 'Default CI Group'
     parallelism: 27
     agents:
-      queue: n2-4
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      localSsds: 1
+      localSsdInterface: nvme
+      machineType: n2-standard-4
     depends_on: build
     timeout_in_minutes: 150
     key: default-cigroup
@@ -31,7 +42,12 @@ steps:
   - command: CI_GROUP=Docker .buildkite/scripts/steps/functional/xpack_cigroup.sh
     label: 'Docker CI Group'
     agents:
-      queue: n2-4
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      localSsds: 1
+      localSsdInterface: nvme
+      machineType: n2-standard-4
     depends_on: build
     timeout_in_minutes: 120
     key: default-cigroup-docker
@@ -44,7 +60,12 @@ steps:
     label: 'OSS CI Group'
     parallelism: 11
     agents:
-      queue: n2-4
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      localSsds: 1
+      localSsdInterface: nvme
+      machineType: n2-standard-4
     depends_on: build
     timeout_in_minutes: 120
     key: oss-cigroup
@@ -57,7 +78,12 @@ steps:
     label: 'Jest Integration Tests'
     parallelism: 3
     agents:
-      queue: n2-4
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      localSsds: 1
+      localSsdInterface: nvme
+      machineType: n2-standard-4
     timeout_in_minutes: 120
     key: jest-integration
     retry:
@@ -68,7 +94,12 @@ steps:
   - command: .buildkite/scripts/steps/test/api_integration.sh
     label: 'API Integration Tests'
     agents:
-      queue: n2-2
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      localSsds: 1
+      localSsdInterface: nvme
+      machineType: n2-standard-2
     timeout_in_minutes: 120
     key: api-integration
 
@@ -79,4 +110,7 @@ steps:
     label: Post-Build
     timeout_in_minutes: 10
     agents:
-      queue: kibana-default
+      image: family/kibana-ubuntu-2004
+      imageProject: elastic-images-prod
+      provider: gcp
+      machineType: n2-standard-2