[WebAssembly] TableGen-erate SDNode descriptions (#166259)
This allows SDNodes to be validated against their expected type profiles
and reduces the number of changes required to add a new node.
CALL and RET_CALL do not have a description in td files, and it is not
currently possible to add one as these nodes have both variable operands
and variable results.
This also fixes a subtle bug detected by the enabled verification
functionality. `LOCAL_GET` is declared with `SDNPHasChain` property, and
thus should have both a chain operand and a chain result. The original
code created a node without a chain result, which caused a check in
`SDNodeInfo::verifyNode()` to fail.
Part of #119709.
Pull Request: https://github.com/llvm/llvm-project/pull/166259
