convert ts-mocha -> mocha for the recently re-added aws-xray propagat…

…or packages

Also add mocha to the top-level devDeps. This had a huge impact on the
package-lock layout: instead of a mocha install in EVERY workspace
subfolder, we get one at the top.

This also resolves some errors in `npm ls` currently on main, that
were introduced in open-telemetry#2269, e.g.:

```
$ npm ls
├─┬ @opentelemetry/[email protected] -> ./propagators/opentelemetry-propagator-instana
│ ├── @types/[email protected] invalid: "10.0.20" from propagators/opentelemetry-propagator-instana
│ ├── [email protected] invalid: "3.1.0" from propagators/opentelemetry-propagator-instana
...
├─┬ @opentelemetry/[email protected] -> ./propagators/opentelemetry-propagator-ot-trace
│ ├── @types/[email protected] invalid: "10.0.20" from propagators/opentelemetry-propagator-ot-trace
...
```