lib: handle Float16Array in node:v8 serdes

[bartlomieju]

This commit adds support for Float16Array in node:v8 serde APIs.

While Float16Array is not available as a global yet (pending stabilization in V8), I "reserved" the next available index for serde purposes so other runtimes, like Deno, that already support Float16Array, can support it in node:v8 serde APIs in a future compatible way.

Closes https://github.com/nodejs/node/issues/55574.