Add half precision floating point support to `StreamPeer`

[pafuent]

Closes godotengine/godot-proposals#5983

Adds put/get methods to StreamPeer that handles half precision floating point values. Adds endode/decode half precision floating point to marshalls.

This PR is rebase into master of #78872. Also I added unit tests to it.

[pafuent]

PackedByteArray already have those: encode_half binded here and implemented here decode_half binded here and implemented here

[radiantgurl]

We should change the title and the topics since now it also modifies FileAccess (core)

[pafuent]

Friendly remainder

[pafuent]

Friendly reminder

[akien-mga]

It's now queued for merging, thanks for your patience :)

[Repiteo]

Thanks!