[std] Implement std.glob() function

[kylewlacy]

This PR adds the new std.glob() function. This uses the new glob recipe type introduced by brioche-dev/brioche#119. Here's a little example inspired by #62:

// Get only the `go.mod` and `go.sum` files from a Go module
std.glob(goModule, ["**/go.mod", "**/go.sum"]);