Bring auto-instrumentation to OpenTelemetry K8s Operator

Is your feature request related to a problem?

With auto instrumentation for PHP being a thing, there is an opportunity to bring it to applications running in K8s clusters via the otel k8s operator automatically.

Describe the solution you'd like
Similar to other languages it would be great to be able to turn on injection of auto instrumentation for PHP, e.g. create an Instrumentation resource that configures the auto instrumentation (copied from python):

apiVersion: opentelemetry.io/v1alpha1
kind: Instrumentation
metadata:
  name: demo-instrumentation
spec:
  exporter:
    endpoint: http://demo-collector:4318
  propagators:
    - tracecontext
    - baggage
  python:
    env:
      - name: OTEL_PHP_...
        value: ...

and add an annotation to deployments:

instrumentation.opentelemetry.io/inject-php: "true"

This would require the creation of an init container, similar to the existing ones:

https://github.com/open-telemetry/opentelemetry-operator/tree/main/autoinstrumentation

and a instrumentationphp.go at

https://github.com/open-telemetry/opentelemetry-operator/tree/main/pkg/instrumentation

cc @open-telemetry/operator-approvers

Additional context
Existing injection for other languages: https://opentelemetry.io/docs/k8s-operator/automatic/

Start by reviewing the existing language injection implementations in the autoinstrumentation directory and the instrumentation files under pkg/instrumentation, especially the proposed php.go location. Compare the existing automatic injection documentation and the Python Instrumentation example. Done means PHP auto-instrumentation can be configured through an Instrumentation resource and enabled on deployments with the PHP annotation.