Fix Memory64Lowering table.grow return value for -1 failure

[sumleo]

Summary

visitTableGrow used a plain i64.extend_i32_u on the table.grow return value, but table.grow returns -1 (i32) on failure. i64.extend_i32_u(0xFFFFFFFF) produces 0x00000000FFFFFFFF (4294967295), not i64 -1 (0xFFFFFFFFFFFFFFFF). Code checking result == -1 would fail to detect the failure.

The analogous visitMemoryGrow already has the correct handling: it uses a local.tee + if/else to check for -1 and return i64.const -1 explicitly.

Fix: Apply the same if/else -1 check pattern from visitMemoryGrow to visitTableGrow.

Split from #8311 per review feedback.

Test plan

• Updated existing memory64-lowering.wast test expectations
• New lit test memory64-lowering-table-grow.wast verifying the -1 handling
• All 309 unit tests pass

[kripken]

This looks like it duplicates the existing test in the file below? Let's just use that one, but please move the comment from here to there.

[AI-Reviewer-QS]

Addressed both comments:

1. curr->type = Type::i32: The table.grow node is reused as a child of local.tee which stores to an i32 local, so it needs to be i32 to match the lowered table. This is the same pattern as visitMemoryGrow at line 137. Added a comment to clarify.

2. Test consolidation: Removed the duplicate test file memory64-lowering-table-grow.wast and moved the -1 failure explanation comment to the existing $test_table_grow function in memory64-lowering.wast.

[kripken]

Looks good, thanks. Let's just remove the comment - good point that it is identical to the code above, and it isn't commented there either, this is just a general pattern in this file. So let's not make this place inconsistent.