box: improve error message raised on hash index replace failure

Old: "Failed to allocate 2147483648 bytes in hash_table for key"
New: "Failed to allocate 16384 bytes in hash_table for key"

ERRINJ_INDEX_ALLOC cannot be used to test this error, because it fails
earlier, so ERRINJ_HASH_INDEX_REPLACE is introduced.

Follow-up #3594

NO_DOC=minor
NO_CHANGELOG=minor