ext/ffi: support alias names for symbol definitions

[DjDeveloperr]

Suggestion

An optional field name (symbol's name) to Foreign Function interface, which would default to the name of key in the function definitions in second parameter.

Why

• Allows making a blocking variant and a non-blocking variant of same symbol. Such as a readFileSync and readFile.
• Allows adding multiple overloads for same symbol. C functions can use varargs to do that. objc_msgSend for example.
• Allows renaming the symbol in some other convention, such as snake_case to camelCase.

Example

const lib = Deno.dlopen("Kernel32", {
  readFileSync: {
    name: "ReadFileA",
    // ...
  },
  readFile: {
    name: "ReadFileA",
    nonblocking: true,
    // ...
  },
  // Still works
  ReadFile: {
    // ...
  },
});