[TVMSCRIPT][TIRx] Preserve parser source spans in IR

[jinhongyii]

Motivation and context

The TVMScript parser already tracks Python AST locations for diagnostics, but TIRx statements and expression results emitted through IRBuilder did not retain those locations. After parsing, a direct intrinsic call, an inlined helper body, or a TilePrimitiveCall therefore could not be traced back to the source range that produced it.

Inline expansion also needs more than a single flat location. The generated IR should retain both the caller location and the helper-definition location, while ordinary nested AST evaluation within one source should not accumulate redundant enclosing spans.

Changes

• Add an active source-span stack to IRBuilder, with scoped push/pop support.
• Make the parser activate the current AST source range while visiting statements and evaluating expressions.
• Attach the active span to emitted TIRx statements and to expression results that do not already carry an explicit span.
• Normalize nested spans from the same source to the innermost relevant range.
• Preserve cross-source inline expansion history as a SequentialSpan, ordered from the call site to the expanded definition.
• Reuse the same source-coordinate calculation for diagnostics and IR spans so their line and column conventions remain consistent.

Source spans remain diagnostic metadata: functions parsed from different source locations keep the same structural hash and remain structurally equal.

Testing

• Verify exact parser source coordinates against diagnostic coordinates.
• Verify spans on direct intrinsic calls and TilePrimitiveCall nodes.
• Verify that inline expansion produces a SequentialSpan containing caller and callee ranges.
• Verify direct IRBuilder.with_source_span behavior.
• Verify that source spans do not affect structural identity.
• Run changed-files pre-commit checks, including clang-format.

Focused result: 9 tests passed.

[gemini-code-assist]

Caution

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