Re-export some VLSIR stuff, particularly sim-related

[dan-fritchman]

Re-export much of the stuff that makes this necessary, in most simulation-invocations:

import hdl21 as h
import vlsirtools.spice as vsp ## <= particularly this part here

A few common ones:

vsp.SimOptions(
        simulator=vsp.SupportedSimulators.NGSPICE, 
        fmt=vsp.ResultFormat.SIM_DATA, #
    )

Some of these might be renamed, but largely they should just be re-exported from vlsirtools.spice to hdl21.sim.

[dan-fritchman]

Running list as they come up:

• SimOptions
• ResultFormat