[TableGen] Use bitwise operations to access HwMode ID. (#88377)

1. Bitwise operations are used to access HwMode, allowing for the
coexistence of HwMode IDs for different features (such as RegInfo and
EncodingInfo). This will provide better scalability for HwMode.
Currently, most users utilize HwMode primarily for configuring
Register-related information, and few use it for configuring Encoding.
The limited scalability of HwMode has been a significant factor in this
usage pattern.
2. Sink the HwMode Encodings selection logic down to per instruction
level, this makes the logic for choosing encodings clearer and provides
better error messages.
3. Add some HwMode ID conflict detection to the getHwMode() interface.