test: Don't sleep before sending data to bash

pexpect has a default delay before sending data, to let applications
turn off TTY echo for example, see
https://pexpect.readthedocs.io/en/stable/commonissues.html?highlight=delaybeforesend#timing-issue-with-send-and-sendline

We don't need this for basically all of our tests, and setting
delaybeforesend to 0 makes running the unit tests around 90% faster,
from 3m18s to 16s on my machine.

In GHA CI, a full run moved from ~22m to ~6m

Author: yedayak

test/t/conftest.py

@@ -272,6 +272,9 @@ def bash(request) -> pexpect.spawn:
             dimensions=(24, 240),
             # TODO? codec_errors="replace",
         )
+        # See https://pexpect.readthedocs.io/en/stable/commonissues.html?highlight=delaybeforesend#timing-issue-with-send-and-sendline
+        # We don't need the delay, and it makes running the tests much slower.
+        bash.delaybeforesend = 0
         bash.expect_exact(PS1)
 
         # Load bashrc and bash_completion