Build WAF enabled NGINX OSS image

[ciarams87]

As a OSS user of NGF who wants to use WAF functionality without Plus
I want an NGINX OSS image instrumented with the NAP WAF module
So that I can enable NAP WAF within my environment without a Plus subscription.

Acceptance criteria:

A NAP WAF enabled image for both OSS can be built locally

Dev Notes:

• NAP WAF alpine version support lags behind the base alpine version of the nginx docker image meaning we cannot use the same base nginx OSS image
• Similarly, the nginx version support lags behind our current OSS image
• This adds further dependency constraints around the Otel and agent modules