Constant folding in EmitPushValue()

[ike709]

Best when combined with #2390 but can be merged independently

Just doing this in Or and And saves 370 BooleanOr opcodes and 352 BooleanAnd opcodes in TG, primarily through funny macros:

if(LAZYACCESS(SSlag_switch.measures, DISABLE_NON_OBSJOBS))
gets compiled to
if((SSlag_switch.measures ? (isnum(5) ? (5 > 0 && 5 <= length(SSlag_switch.measures) ? SSlag_switch.measures[5] : null) : SSlag_switch.measures[5]) : null))
which const folds to
if((SSlag_switch.measures ? (isnum(5) ? (5 <= length(SSlag_switch.measures) ? SSlag_switch.measures[5] : null) : SSlag_switch.measures[5]) : null))
which saves a GreaterThan and BooleanAnd on every LAZYACCESS()

[ike709]

TODO: Need to cast Number.Value to int in operators like modulo; we already do this at runtime but TryAsConstant() just operates on the floats.

[ike709]

TODO: Go through the Builtins.cs expressions too

[ZeWaka]

#885 my child