[Test] Restore shadowed duplicate test functions in relax/runtime tests

[Anai-Guo]

Several relax/runtime test modules define the same test function name twice. The second def rebinds the module-level name, so pytest only collects the later one and the earlier test silently never runs. File-level # ruff: noqa: F811 headers were hiding the lint signal (ruff check --select F811 --ignore-noqa shows them).

File	Duplicate	Fix
relax/test_expr.py	test_match_cast (two different tests)	Rename the second to test_match_cast_json_roundtrip. The restored first test still used the removed MatchCast.pattern field → switched to b.ty.shape[i].same_as(m).
relax/test_ast_printer.py	test_shape_expr (symbolic vars vs. constants)	Rename the first to test_shape_expr_symbolic. ShapeExpr now requires int64 values, so the vars are int64 and the expected printout is Expr(value=`m`).
runtime/test_runtime_nd_array.py	test_1d_view_of_first_half_of_1d_arr	The second one uses relative_byte_offset=512 * 4 → rename to test_1d_view_of_second_half_of_1d_arr (mirrors the existing 2d pair).
relax/test_transform_gradient_checkpoint.py	test_checkpoint_dag	The second copy — the one pytest was collecting — is truncated: it builds the function but has no Expected module and no assert_structural_equal. Removed it so the full test runs.
relax/test_analysis.py	test_reshape_pattern_reject_reduction	Byte-identical second copy removed.
relax/test_analysis_well_formed.py	test_incomplete_ty_must_be_consistent	Byte-identical second copy removed.

F811 is dropped from the file-level noqa headers that no longer need it (otherwise RUF100 fires).

Left alone: test_op_gradient_numeric.py::test_reshape has the same issue, but it is LLVM-gated and I could not run it locally, so it is not included here.

Testing

CPU build of current main (ccd98e9, USE_LLVM OFF), pytest per file:

File	before	after
relax/test_expr.py	31 passed	32 passed
relax/test_ast_printer.py	24 passed	25 passed
runtime/test_runtime_nd_array.py	14 passed	15 passed
relax/test_transform_gradient_checkpoint.py	11 passed	11 passed (test_checkpoint_dag now includes the structural-equality check)
relax/test_analysis.py	37 passed	37 passed
relax/test_analysis_well_formed.py	57 passed, 2 xfailed	57 passed, 2 xfailed

Without the two small updates, the restored test_match_cast fails with AttributeError: 'MatchCast' object has no attribute 'pattern' and test_shape_expr_symbolic fails with the value in ShapeType can only have dtype of int64, i.e. both had drifted while hidden.

ruff check / ruff format --check (v0.12.3, repo config) pass on all six files.

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