Proposal: move lib/util to lib/os/process

[puellanivis]

The package name “utils” is devoid of specific meaning or purpose. It has long been known that this is a bad idea, and well argued.

However, the current lib/util provides a relatively concise group of concepts around handling process lifetimes, and can be packaged up and moved to a meaningful package name:

• AtExit/Exit functionality.
• a process-level Context, HangupChannel support, as well as Shutdown (now Quit)
• Version and versioning in general
• • Change versioning to use a Semver string (which build systems could then inject).
• • Remove embedded BUILD in favor of passing a Buildstamp into package.
• Collecting all this together into a convenient Init function.