Add low-resolution wrappers for timing functions

[danfinlay]

We should not provide high-resolution timers to plugins, but some plugins do require a sense of time. For those, we should provide a low-resolution access to time, and probably make it a permission, too.

Added timers for beta purposes (ethers uses timers to monitor transaction completion) in https://github.com/MetaMask/metamask-snaps-beta/pull/134

[kumavis]

i assume this is related to timing attacks, including spectre style vulns