Add support for any arbitrary key from Pod Spec Template to CRD

[gecube]

Hi!

I don't want to create a bunch of issues, but I see that dragonflydb CRD is very basic and does not allow to customize many things that are mandatory. Otherwise it is very difficult to use it when you are getting out of some standard scenario.

Like #197 - if images are stored in private registry
or #257 for securityContext and podSecurityContext

Right now the only option is to use some mutation hook like Kyverno and patch the pod spec on the fly...

[gecube]

Also it would be nice to disallow enableServiceLinks... They usually are not very useful and even more - we got the bug in cnpg operator when TOO much services were deployed into one particular namespace like here cloudnative-pg/cloudnative-pg#6234

It is why we need have an option to control ANY parameter of Pod Spec template.

[Pothulapati]

@gecube

It makes sense to add this!