compile xmtp_id and xmtp_mls to wasm32

[insipx]

• feature flag/Send bounds

• slightly changes streams. All streams except for _with_callback are stack-based/no more Box<Stream>. This makes it easier to modify the Send bound for wasm32.

• general dependency pruning where possible.

  • Remove the smart-default crate since it was used in only one place.
  • replace flume with tokio::sync::mpsc

• blocked on some missing trait implementations for WasmSqlite backend which require a patched diesel.

• remove InboxOwner in xmtp_mls and use the one in xmtp_id

  • this allows us to remove xmtp_mls dependency on ethers. xmtp_id depends on ethers anyway

• remove ethers_core and use the ethers::core re-export

90% of this PR is adding cfg/cfg_attr to tests/items + hoisting individual types like Box<dyn Signature> into type alias to make it possible to vary Send/Sync bounds based on wasm/not wasm

closes #951 closes #939 closes #940

this PR makes tests compile in WebAssembly, but not necessarily pass. Rel: #941

[insipx]

wasm_timer uses normal std SystemTime libraries if on native, and the JS web_sys/js_sys shim if on web

[insipx]

I preferred the implementation in xmtp_id, enabling us to remove the ethers dependency in xmtp_mls

[insipx]

this should be a minor performance improvement, streams are entirely stack-based, even in the with_callback methods.