[WebAssembly] Change catch_all's opcode

We decided to change `catch_all`'s opcode from 0x05, which is the same
as `else`, to 0x19, to avoid some complicated handling in the tools.

See: https://github.com/WebAssembly/exception-handling/issues/147

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D96863