feat(helm): Add PodDisruptionBudget option to helm chart

[SgtCoDFish]

This brings the agent into line with many other open source charts (see e.g. cert-manager).

We document this as a best practice here:
https://docs.venafi.cloud/vaas/k8s-components/c-k8s-components-best-practice/#poddisruptionbudget

This is largely adapted from https://github.com/cert-manager/trust-manager/tree/main/deploy/charts/trust-manager !

[sitaramkm]

@SgtCoDFish I could be seeing this wrong - I am running version 0.1.45 atm. Your proposed changes need to go into 46? Or is there some inconsistency in the versions someplace?

[SgtCoDFish]

I could be seeing this wrong - I am running version 0.1.45 atm. Your proposed changes need to go into 46? Or is there some inconsistency in the versions someplace?

I think this is because I ran make update-helm-docs which picked up the latest version number. I'm not actually proposing to change the version number in this PR (which would involve a change to Chart.yaml) - we'll bump that later.

Basically I think I'm just bringing the docs up to date here, not changing the version number.

[SgtCoDFish]

note: version bumps come from running make update-helm-docs - looks like they weren't bumped previously!

[SgtCoDFish]

Cheers Olu!