Support older pinned versions of Spin

[kate-goldenring]

Should we support older pinned versions of Spin?

A brew install fermyon/tap/spin will always install latest but specific versions could be targeted with brew install fermyon/tap/spin@N where V is version (i.e. 1.3). Each older pinned version would live in it's own formula named [email protected].

How do we ensure that a pinned version install conflicts with a latest version already installed? Homebrew supports a conflicts_with directive but it seems more targeted at other brew packages rather than the native binary.

Many projects only support latest, like Nomad as discussed here.