Remove pkg/util

[hasheddan]

This issue has been created to track the work originally expressed in crossplane/crossplane#448

It's generally considered a mispattern in the Go world to create package names like util, or common. The preferred alternatives are typically one or more of:

• Breaking out functions into targeted packages with self documenting names like strings, metadata, etc.
• Tolerating the existence of duplicate instances of simple utility functions like util.ToLowerRemoveSpaces defined closer to where they're used.
• Avoiding such extremely simple utility functions altogether.

Sources:

• https://blog.golang.org/package-names (See "Bad package names")
• https://dave.cheney.net/2019/01/08/avoid-package-names-like-base-util-or-common
• https://rakyll.org/style-packages/

[negz]

As of #112 we're down to two functions left in pkg/util:

• GeneratePassword is used by a handful of cache and database managed resource controllers, and the latter is used by all bucket controllers. We might consider replacing it with https://godoc.org/github.com/sethvargo/go-password/password#MustGenerate
• ConditionalStringFormat is used by the bucket controllers. I believe it's only used to set bucket names, and should thus be replaced by the crossplaneio/external-name annotation once we bump those controllers to the crossplane-runtime managed resource reconciler.