Add an option to select how to seed random()

[dcodeIO]

This adds an option to asc to select how to seed native math's random() function, currently supporting:

  --seedRandom          Sets the randomness source used by Math.random. Defaults to
                        a compile-time constant while emitting a warning.

                         const     Compile-time constant without a warning.
                         12345     Custom constant without a warning.
                         date      Imports 'Date' from JS and calls Date.now()
                         math      Imports 'Math' from JS and calls Math.random()
                         wasi      Uses the respective WASI interface.
                         ...       Internal name of a custom function returning i64.

[dcodeIO]

This will probably fail somewhere due to randomness in fixtures. Also makes me wonder if we should remove NativeMath.seedRandom because if one uses it explicitly, there'll still be a warning.

[dcodeIO]

There's something wrong here in that "./bindings/wasi" does not work. Can't find the symbols. Thought we had fixed those export * / import * problems :(

[dcodeIO]

By doing that, we can changetype<ArrayBufferView> anything accessing .dataStart, getting rid of TS syntax highlighting issues.

[MaxGraey]

It seems use Long.fromBits here is unnecessary. What about:

const low = Math.random() * 0xffffffff >>> 0;
const high = Math.random() * 0xffffffff >>> 0;
assemblyscript.setGlobalAlias(compilerOptions, "ASC_SEEDRANDOM_LOW", low.toString());
assemblyscript.setGlobalAlias(compilerOptions, "ASC_SEEDRANDOM_HIGH", high.toString());

[dcodeIO]

Superseded by #1159 which adds a programmatic mechanism instead.