[tosa_mlir_translator] Add FP8 support

Add serialization and deserialization support for FP8 data types.
Also, added deserialization support for BF16 constants.
BF16 and FP8 constants are serialized and deserialized as F32 values.

Signed-off-by: Tai Ly <tai.ly@arm.com>
Change-Id: I919acd82dc5e0b85024b6403d9623eaa26151aef