Support a `Stream` instead of `string` buffer

[rLindorfer]

Current Situtation

The Scanner class which is used to return tokens from the input buffer currently only accepts a string.

public Scanner(string buffer)
{
    Buffer = buffer ?? throw new ArgumentNullException(nameof(buffer));
    Cursor = new Cursor(Buffer, TextPosition.Start);
}

This means, if we read this stream from a blob or a file, we initially have to allocate the entire string in memory.

Problem

A huge buffer string will end up on the LOH (large object heap) which can lead to several memory and performance problems.
https://learn.microsoft.com/en-us/dotnet/standard/garbage-collection/large-object-heap

Solution

Use a generic Stream instead of a plain string. As a result, it would be possible to directly stream the buffer from a blob or a file.
As a result, it would for example be possible to implement a streaming support for parsing (Fluid) templates.

[sebastienros]

I shared my thoughts on this other issue

sebastienros/jint#2092 (comment)