rework I/O stream abstractions

[andrewrk]

The main goal here is to make the function pointers comptime, so that we
don't have to do the crazy stuff with async function frames.

Since InStream, OutStream, and SeekableStream are already generic
across error sets, it's not really worse to make them generic across the
vtable as well.

See #764 for the open issue acknowledging that using generics for these
abstractions is a design flaw.

See #130 for the efforts to make these abstractions non-generic.

This commit also changes the OutStream API so that write returns
number of bytes written, and writeAll is the one that loops until the
whole buffer is written.

[andrewrk]

With these changes, here's an example of what reading from buffered stdin looks like:

 const std = @import("std");
 
 pub fn main() anyerror!void {
-    var stdin_unbuf = std.io.getStdIn().inStream();
-    // damn that is pretty painful, isn't it?
-    const in = &std.io.BufferedInStream(@typeOf(stdin_unbuf).Error).init(&stdin_unbuf.stream).stream;
+    const in = std.io.bufferedInStream(std.io.getStdIn().inStream()).inStream();
 
     var sum: u64 = 0;
     var line_buf: [50]u8 = undefined;

[andrewrk]

@mlarouche - in ed13cff I attempted to fix the ELF emit raw code, but I didn't test it yet. Want to give it a lookover (and possibly submit a fix against this branch?) otherwise, I'll try to run zig build on https://github.com/wendigojaeger/ZigGBAHelloWorld to test it tomorrow before merging this branch.

[mlarouche]

@mlarouche - in ed13cff I attempted to fix the ELF emit raw code, but I didn't test it yet. Want to give it a lookover (and possibly submit a fix against this branch?) otherwise, I'll try to run zig build on https://github.com/wendigojaeger/ZigGBAHelloWorld to test it tomorrow before merging this branch.

I fixed those compile errors when trying to branch (see attached patch) but emit_raw is still completly broken, I don't have time until tonight to fix it properly so feel free to fix it during the day

0001-Fix-compile-with-emit_raw.txt

[LemonBoy]

There are a few compilation errors, a few typos (shdr vs phdr), the code is corrupting section_headers while iterating over it...

[andrewrk]

Notable in this branch is the new std.io.StreamSource abstraction, which is a non-generic data type that can be used to abstract across both memory buffers and files. Usage example here: zigimg/zigimg#41

[mlarouche]

Confirmed that latests changes work with ZigGBA

[mlarouche]

Also isn't #130 to make those interface generics instead ?

[andrewrk]

nah, the whole point of a vtable language feature is to provide an interface type which is not generic, but can be used in different contexts with different implementations