- Use tostring() as that's what print() uses internally.
- Do not append trailing new line.

Problem:
Using `meths.exec2("code", { output = true })` is too verbose.

Solution:
Use exec_capture() in more places.

Problem:
The signature of nvim_exec() is not extensible per ":help api-contract".

Solution:
Introduce nvim_exec2() and deprecate nvim_exec().

It is less likely for client to exit between jobstart() and jobwait() if
they are invoked in the same RPC request instead of two separate ones.

Problem:
1. CI logs have too many (40+) logs mentioning SIGHUP:
   ```
   WRN 2022-06-18T16:05:47.075 T3568.22499.0/c deadly_signal:177: got signal 1 (SIGHUP)
   WRN 2022-06-18T16:05:47.273 T3569.91095.0/c deadly_signal:177: got signal 1 (SIGHUP)
   WRN 2022-06-18T16:05:47.651 T3570.59545.0/c deadly_signal:177: got signal 1 (SIGHUP)
   ```
2. TS parser test still sometimes fails on BSD CI.
3. remote_spec test fails too often.

Solution:
1. Log deadly signals at INFO level. It hasn't been helpful in CI, and
   for local troubleshooting it's reasonable to adjust the loglevel as
   needed.
2. Adjust the TS parser test again. ref #18911
3. Skip the remote_spec test. The `--remote` feature was merged before
   it was fully formed and needs to be revisited.

Clean up lint errors, too

This also fixes a fair number of issues found in running the tests