Problem:
1. Log messages (especially in CI) are hard to correlate with tests.
2. Since b353a5c05f#11886, dumplog() prints the logs next to test
failures. This is noisy and gets in the way of the test results.
Solution:
1. Associate an incrementing id with each test and include it in log
messages.
- FUTURE: add v:name so Nvim instances can be formally "named"?
2. Mention "child" in log messages if the current Nvim is a child (based
on the presence of $NVIM).
BEFORE:
DBG … 12345 UI: event
DBG … 12345 log_server_msg:722: RPC ->ch 1: …
DBG … 12345 UI: flush
DBG … 12345 inbuf_poll:444: blocking... events_enabled=1 events_pending=0
DBG … 23454 UI: stop
INF … 23454 os_exit:594: Nvim exit: 0
AFTER:
DBG … T57 UI: event
DBG … T57 log_server_msg:722: RPC ->ch 1: …
DBG … T57 UI: flush
DBG … T57 inbuf_poll:444: blocking... events_enabled=1 events_pending=0
DBG … T57/child UI: stop
INF … T57/child os_exit:594: Nvim exit: 0