[TableGen] Improvements to Named operands in InstrInfoEmitter (#124960)

- Assign `OpName` enum values in the same alphabetical order in which
they are emitted.
- Get rid of OPERAND_LAST which is not used anywhere.
- Inline `initOperandMapData` into `emitOperandNameMappings` to help see
clearly how various maps are computed.
- Emit the static `OperandMap` table as int8_t when possible. This
should help reduce the static size by 50% in the common case.
- Change maps/vectors to use StringRef instead of std::string to avoid
unnecessary copies.

0 files changed, 0 insertions, 0 deletions