fix: properly catch sigterm sent from global (#6724)
### Description
Global `turbo` sends a `SIGTERM` to local `turbo` when it receives any
of `SIGINT`/`SIGTERM`/`SIGHUP` and local `turbo` only had signal
handlers setup for `SIGINT`. This PR adds a signal handler for the
`SIGTERM` that gets sent.
Immediate future work is plumbing the differing signals down to the
process manager. The process manager currently only allows for sending
`SIGINT` to child process. I just wanted to get this out the door ASAP
to get us into a better state.
Future work will be reworking the global `turbo` signal handling so that
we forward the correct signals to local `turbo`.
### Testing Instructions
Send a `SIGTERM` to `turbo` and make sure that the signal handler gets
triggered:
```
# with binary built off of main
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $ pstree 46675
-+= 46675 olszewski /Users/olszewski/code/vercel/turborepo/target/debug/turbo dev
|-+= 46712 olszewski node /Users/olszewski/.nvm/versions/node/v16.18.1/bin/pnpm run dev
| \-+- 46726 olszewski node /private/tmp/ctrl-c-test/apps/docs/node_modules/.bin/../next/dist/bin/next dev --port 3001
| \--- 46757 olszewski next-server
\-+= 46713 olszewski node /Users/olszewski/.nvm/versions/node/v16.18.1/bin/pnpm run dev
\-+- 46739 olszewski node /private/tmp/ctrl-c-test/apps/web/node_modules/.bin/../next/dist/bin/next dev
\--- 46758 olszewski next-server
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $ kill 46675
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $ lsof -i :3000
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
node 46758 olszewski 16u IPv6 0xed7930af6ecc15d3 0t0 TCP *:hbci (LISTEN)
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $
# with changes in this PR
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $ pstree 38435
-+= 38435 olszewski /Users/olszewski/code/vercel/turborepo/target/debug/turbo dev
|-+= 38472 olszewski node /Users/olszewski/.nvm/versions/node/v16.18.1/bin/pnpm run dev
| \-+- 38501 olszewski node /private/tmp/ctrl-c-test/apps/docs/node_modules/.bin/../next/dist/bin/next dev --port 3001
| \--- 38512 olszewski next-server
\-+= 38473 olszewski node /Users/olszewski/.nvm/versions/node/v16.18.1/bin/pnpm run dev
\-+- 38488 olszewski node /private/tmp/ctrl-c-test/apps/web/node_modules/.bin/../next/dist/bin/next dev
\--- 38513 olszewski next-server
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $ kill 38435
[0 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $ lsof -i :3000
[1 olszewski@chriss-mbp] /Users/olszewski/code/vercel/turborepo $
```
Closes TURBO-1858
---------
Co-authored-by: Chris Olszewski <Chris Olszewski>
