Add 8 bit to quantization data type

[ZiyueXu77]

Fixes FLARE-2374 .

Description

This QA report has an 8 bit input, and previously we have not include it in the valid datatype, but since now we have 4 bit schemes, it makes sense to add it to the original datatype

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Quick tests passed locally by running ./runtest.sh.
• In-line docstrings updated.
• Documentation updated.

[ZiyueXu77]

/build