Add bcrypt export format

**Describe the problem/challenge you have**

As a [secretgen-controller](https://github.com/carvel-dev/secretgen-controller) user
In order to use a generated secret in workloads that expect bcrypt encoded password
I need the SecretTemplate to support a bcrypt export format beyond base64 encoding

**Describe the solution you'd like**
[A clear and concise description of what you want to happen. If applicable a visual representation of the UX.]

SecretTemplate to support an additional `format` field with default `base64` and an additional `bcrypt` value

See
https://github.com/carvel-dev/secretgen-controller/blob/a09e1b8d755e19cee8f54881b0e6122777850b59/docs/secret-template.md?plain=1#L49-L53

> In order to login to the WGE UI, you need to generate a bcrypt hash for your chosen password and store it as a secret in the Kubernetes cluster.
>
> There are several different ways to generate a bcrypt hash, this guide uses gitops get bcrypt-hash from our CLI, which can be installed by following the instructions [here](https://docs.gitops.weave.works/docs/installation/weave-gitops-enterprise/#gitops-cli).
>

**Anything else you would like to add:**

https://docs.gitops.weave.works/docs/installation/weave-gitops-enterprise/#6-configure-password

Similar request on ytt in https://github.com/carvel-dev/ytt/issues/106

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