This adds two clock interfaces: sys.Walltime and sys.Nanotime to
allow implementations to override readings for purposes of security or
determinism.
The default values of both are a fake timestamp, to avoid the sandbox
break we formerly had by returning the real time. This is similar to how
we don't inherit OS Env values.
This notably changes NewRuntimeJIT to NewRuntimeCompiler as well renames
packages from jit to compiler.
This clarifies the implementation is AOT, not JIT, at least when
clarified to where it occurs (Runtime.CompileModule). In doing so, we
reduce any concern that compilation will happen during function
execution. We also free ourselves to create a JIT option without
confusion in the future via CompileConfig or otherwise.
Fixes#560
Signed-off-by: Adrian Cole <adrian@tetrate.io>
