consolidate various field validations with what is already done in shipwright-io/build

[gabemontero]

Started seeing some overlap in validation individual PRs are doing in this repo with what is already done is spots like https://github.com/shipwright-io/build/blob/main/pkg/validate/

Do we just halt / remove doing analogous validations in the CLI?

Or do we create a common shared package of validations that can be used in both repos?

See a5a8cd8#r703641375 for a specific discussion thread / example.

[adambkaplan]

An item of concern - we need to ensure the validations we need to consume are exportable from the validate package. This can be tested now that cli depends on the build module.