compat: Buffer: allow optional positional arguments to be undefined

[kitsuned]

What does this PR do?

SSIA.
Fixes Buffer.prototype.copy() and Buffer.prototype.compare() in the following cases:

Buffer.prototype.copy()

Welcome to Node.js v18.17.1.
Type ".help" for more information.
> Buffer.alloc(0).copy(Buffer.alloc(0), undefined)
0

Welcome to Bun v1.0.0
Type ".help" for more information.
> Buffer.alloc(0).copy(Buffer.alloc(0), undefined)
1 | "use strict";void 0;Buffer.alloc(0).copy(Buffer.alloc(0), undefined);
                       ^
TypeError: Expected number

Buffer.prototype.compare()

Welcome to Node.js v18.17.1.
Type ".help" for more information.
> Buffer.alloc(0).compare(Buffer.alloc(0), undefined)
0

Welcome to Bun v1.0.0
Type ".help" for more information.
> Buffer.alloc(0).compare(Buffer.alloc(0), undefined)
1 | "use strict";void 0;Buffer.alloc(0).compare(Buffer.alloc(0), undefined);
                       ^
TypeError: Expected number

[Jarred-Sumner]

thank you for this

later we should do a helper for argumentCount() that is "last non-undefined argument", since it's really easy to make a mistake like this in native code

[kitsuned]

hey, @Jarred-Sumner! any updates on this?

fyi quite popular tar-stream package is broken due to Buffer handling in b4a dependency.
the PR addresses this issue.