[Objcopy][Wasm] Allow selecting known sections by name

Currently, only custom sections can be selected by operations that use section
names, because only custom sections have explicit names (whereas known sections
have names defined by the spec and only use their indices in the binary format).
This CL makes objdopy use the spec-defined names for these sections, allowing
them to be used in operations such as dumping and removal.

This is a prerequisite for fixing
https://github.com/emscripten-core/emscripten/issues/13084

Differential Revision: https://reviews.llvm.org/D126509