fix: correct type mismatch in BinaryEncoder write

[zhongyujiang]

Rationale for this change

Some fsspec write implementations expect the input data to be bytes, such as in JuiceFS: https://github.com/juicedata/juicefs/blob/main/sdk/python/juicefs/juicefs/juicefs.py#L514.
But currently, some places in BinaryEncoder use bytearray, which can cause exceptions when writing the manifest.

raise TypeError(f"a bytes-like object is required, not '{type(data).__name__}'")
TypeError: a bytes-like object is required, not 'bytearray'

I ran into this issue while adding Juice filesystem support, so this PR fixes the data type written by BinaryEncoder to bytes in order to resolve it.

Currently, pyiceberg.io.OutputStream.write is also annotated to accept data of type bytes.

Are these changes tested?

It seems that the filesystems currently supported in pyiceberg do not strictly require the write input to be of type bytes, so I didn’t add a test. I tested this on our internal Juice filesystem, and it works.

Are there any user-facing changes?

No

[Fokko]

Thanks @zhongyujiang for cleaning this up 👍