Reenable disassembler

[fengb]

Now that we have a separate decoder, the disassembler should be much easier.

[fengb]

Core functionality is now done. Still debating on how to communicate into JS.

Input:

• u32 — hides intent, upstream byte packing
• [*]u8 — communicates intent, upstream allocation
• u8, u8, u8 — communicates intent, lots of args!

Output:

• struct { [*:0]const u8, inst_length: u32 } — new data type, temporary storage
• struct { [*]const u8, len: u16, inst_length: u16 } — new data type, temporary storage
• U8Chunk — squeeze duration into first char, temporary storage
• buf: [*]u8 -> U8Chunk — squeeze duration into first char, upstream storage

I think we need to make a concession on the output format. Since we need to return both a "slice" and an instruction length, there's not a nice way of squeezing both into a u64.

[fengb]

Mostly complete by 97ceb70deeafb276bc9edad67a82541c024c8ec3. We still need to reenable CB operations.

[fengb]

Also... @tagName(Op.Id) increases the bundle size by ~15 KB (4 KB gzipped) due to extra string literals + dispatch table. Sad panda.