[BUG] Canonicalize noncanonical BOOL8 values in murmurhash3_x86_32

[PointKernel]

Describe the bug

Follow-up from #23265 and review discussion #23265 (comment).

cuDF documents BOOL8 as 0 == false, else true, but cudf::hashing::murmurhash3_x86_32 can hash noncanonical stored bytes such as 2 or 255 as their raw values instead of canonicalizing them to 1. Logically equivalent true values can therefore produce different hashes.

Steps/Code to reproduce bug

1. Construct a BOOL8 column directly from raw bytes containing {0, 1, 2, 255}. A raw column is required because cudf::test::fixed_width_column_wrapper<bool> canonicalizes values during construction.
2. Hash the column with cudf::hashing::murmurhash3_x86_32.
3. Compare the results for stored bytes 1, 2, and 255.

The existing boolean specialization converts the stored value directly to uint32_t, allowing noncanonical representations to remain distinct.

Expected behavior

Every nonzero BOOL8 value represents true and should be canonicalized to 1 before hashing. Stored bytes 1, 2, and 255 should produce identical hashes for the same seed.

Add explicit canonicalization (key ? 1 : 0) and regression coverage constructed from raw BOOL8 bytes.