[bindings] Drop the lifetime bound on `Record` for bindings builds

Because log `Record`s are now being passed by ownership to `log`,
the bindings get quite annoyed that there's a lifetime hanging
around. We already don't use this lifetime in bindings (the
`FormatArgs` is converted to a string and stored on the heap), so
we can just drop the lifetime, even though it requires some
macro'ing of the struct definition to do so.