[DataType] Update to use explicit Bool Type Aligning with DLPack

[tqchen]

This PR updates the project to use explicit bool type which helps us to align with dlpack. It will also streamline explicit use of bool types.

[gemini-code-assist]

Summary of Changes

Hello @tqchen, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant refactoring of how boolean data types are handled within the project. By transitioning from an implicit representation (1-bit unsigned integers) to an explicit kDLBool type, the project enhances its alignment with the DLPack standard. This change streamlines the definition, checking, and processing of boolean types across the runtime, TIR, and code generation components, ensuring more robust and explicit type handling throughout the system.

Highlights

• Explicit Boolean Type Introduction: The project now uses an explicit kDLBool type to represent booleans, aligning with the DLPack standard. Previously, booleans were implicitly represented as 1-bit unsigned integers (kUInt with bits=1).
• DataType Class Updates: The DataType class in include/tvm/runtime/data_type.h has been updated to include kBool in its TypeCode enum. The is_bool() method now directly checks for kBool, and a new is_predicate_dtype() method has been added to handle both kBool and 1-bit unsigned integers for predicate expressions. The DataType::Bool() constructor now explicitly creates a kDLBool type with 8 bits.
• TIR Operations and Constant Folding: TIR operations like const_true() and const_false() now leverage the new explicit DataType::Bool(). Constant folding logic for comparison and bitwise operators has been updated to return DataType::Bool() results. Additionally, MakeConstScalar and various type-checking functions for bitwise operations now explicitly support the is_bool() type.
• Code Generation Updates: LLVM and SPIRV code generation backends have been adapted to recognize and correctly handle the new explicit boolean type. This includes mapping kDLBool to LLVM's 1-bit integer type (t_int1_), and updating type declarations, casting rules, and comparison operations in SPIRV to use DataType::Bool().
• Python Bindings and Tests: Python bindings and various test cases across arith, relax, and tir modules have been modified to reflect the change, using dtype='bool' instead of dtype='uint1' where appropriate, ensuring consistency with the new explicit boolean type.

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[gemini-code-assist]

Code Review

This pull request introduces an explicit bool type to align with DLPack, replacing the previous uint1 representation. The changes are extensive and consistently applied across the codebase, including data type definitions, operator implementations, constant folding, and tests. The introduction of is_predicate_dtype is a good way to maintain backward compatibility during this transition.

I've found a couple of minor issues:

1. A copy-pasted Doxygen comment in data_type.h.
2. Inconsistent use of DataType::Bool() and DataType::Bool(1) in const_fold.h.

Overall, this is a solid refactoring that improves type safety and clarity. My review comments provide suggestions to address the minor issues.