[llvm] [Object][Wasm] Move wasm Object tests into their own directory (NFC) (PR #81072)

[Derek Schuff via llvm-commits]

dschuff wrote:

I looked at this a little more. 
Regarding Wasm vs WebAssembly: I don't think naming the directory WebAssembly is a good idea. We have several files and directories named `Wasm` or `wasm` (e.g. lib/Object/Wasm, lld/wasm) and they (almost) all refer to the binary/object format, as opposed to the architecture. Naming just this test directory WebAssembly would make things worse rather than better IMO (because regardless of whether you believe it's good that the bin format doesn't match the architecture, at least right now we are mostly consistent).

Regarding Wasm vs wasm: It looks like actually Wasm is more common than wasm (notable exceptions being lld/wasm and  llvm/lib/ObjCopy/wasm). It also looks like `ninja check-llvm-object-wasm` works with Wasm as the directory name.

Therefore for this PR I'm going to suggest keeping the name as Wasm. Fixing some `wasm` and `WASM` directories to match can be a followup PR.

https://github.com/llvm/llvm-project/pull/81072