This patch gets rid of the Globals! Now we have "true" Data symbols, as requested by Sam.
And, there's an explicit symbol table.
All tests pass (after some updates). Function bodies and relocations etc have not changed, which adds confidence that it's working.
First half of symbol table support: D41954
Must be committed along with the corresponding LLD change: D42585
Implements: https://github.com/WebAssembly/tool-conventions/pull/39
This separation of GlobalType looks good, but can perhaps be standalone change unrelated to symbols?