Bump wasmtime from 14.0.4 to 18.0.2 in /native/wasmex

Bumps [wasmtime](https://github.com/bytecodealliance/wasmtime) from 14.0.4 to 18.0.2.
- [Release notes](https://github.com/bytecodealliance/wasmtime/releases)
- [Changelog](https://github.com/bytecodealliance/wasmtime/blob/main/docs/WASI-some-possible-changes.md)
- [Commits](bytecodealliance/wasmtime@v14.0.4...v18.0.2)

---
updated-dependencies:
- dependency-name: wasmtime
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>