Make apm-attacher image a multi-arch image - arm based image

[mpakoupete]

Is your feature request related to a problem? Please describe.

I'm interested in using APM attacher on ARM based worker nodes. It seems not supported
I tested that and here is the error I get :

  Type     Reason     Age                From               Message
  ----     ------     ----               ----               -------
  Normal   Scheduled  31s                default-scheduler  Successfully assigned elastic-apm/elastic-webhook-c58bb4b7-9lwm7 to gke-mawaki-eck-arm-lab-default-pool-165b8259-19j8
  Normal   Pulled     30s                kubelet            Successfully pulled image "docker.elastic.co/observability/apm-attacher:v1.1.1" in 824ms (824ms including waiting). Image size: 9987324 bytes.
  Normal   Pulled     29s                kubelet            Successfully pulled image "docker.elastic.co/observability/apm-attacher:v1.1.1" in 223ms (223ms including waiting). Image size: 9987324 bytes.
  Normal   Pulling    14s (x3 over 31s)  kubelet            Pulling image "docker.elastic.co/observability/apm-attacher:v1.1.1"
  Normal   Created    14s (x3 over 30s)  kubelet            Created container elastic-webhook
  Normal   Started    14s (x3 over 30s)  kubelet            Started container elastic-webhook
  Normal   Pulled     14s                kubelet            Successfully pulled image "docker.elastic.co/observability/apm-attacher:v1.1.1" in 183ms (183ms including waiting). Image size: 9987324 bytes.
  Warning  BackOff    13s (x3 over 29s)  kubelet            Back-off restarting failed container elastic-webhook in pod elastic-webhook-c58bb4b7-9lwm7_elastic-apm(a499e778-3354-4433-a4c9-85aec398b1cb)

Looking into the logs :

exec ./webhook: exec format error

Describe the solution you'd like

Make apm-attacher image an arm based image