Global.serialize function to serialize instance of any type

[kushti]

Implement Global.serialize function with SAny -> SByteArray signature to serialize an instance of any type.

It is replacing following existing PRs:

#982 (just started)
#984 (just started)
#974

Header serialization can be found in #974

Do round-trip tests against Global.deserialize[T] from #979

[aslesarenko]

It is replacing following existing PRs:

#982 (just started) #984 (just started)

@kushti, it may still be useful to have a separate Numeric.toBytes method because generic serialize produces ZigZag encoded bytes for numeric types.

We can call it Numeric.toBigEndianBytes.

This will be consistent with the existing longToByteArray, byteArrayToLong, byteArrayToBigInt, but will work for all numeric types.