Move the WasmSymbolInfos from their own vector on the WasmLinkingData
directly into the WasmSymbol object. Removing the const-ref to an
external object allows the vector of WasmSymbols to be safely
expanded/reallocated; generating symbol info from the name section will
require this, as the numbers of function and data segment names are
stored separately.
This is a step toward generating symbol information from name sections
for #76107
ef1f999e13