Improve dependency gating on objdiff-core (#126)

* Reduce dependencies for no features

* Add missing deps to every feature

* Add missing `dep:`s

* Gate even more deps behind features

Removes dependency on tsify-next / wasm-bindgen unless
compiling with the wasm feature by using `#[cfg_attr]`

* Fix wasm

---------

Co-authored-by: Luke Street <luke@street.dev>

objdiff-core/src/obj/read.rs

@@ -64,6 +64,7 @@ fn to_obj_symbol(
     if obj_file.format() == BinaryFormat::Elf && symbol.scope() == SymbolScope::Linkage {
         flags = ObjSymbolFlagSet(flags.0 | ObjSymbolFlags::Hidden);
     }
+    #[cfg(feature = "ppc")]
     if arch
         .ppc()
         .and_then(|a| a.extab.as_ref())