Allow users to override Bazel's 120s connect timeout

Bazel constrains starting up and connecting to a local server to 120s.  This
occasionally causes problems for us on heavily loaded, high numcpu machines,
because the Bazel client+server may end up starved out via simple CPU
contention.  (Where we observed startup timeouts, machines had plenty of RAM,
I/O looked normal---procs weren't stuck in disk wait---but the run queues were
60+.)

Mitigate this by introducing a new startup option, `--local_startup_timeout_secs`,
which allows users to specify their own timeout values.  (Note:  I primarily
used `connect_timeout_secs` as a reference.)

TODO: Consult Bazel team to add test case per comments in
[bazel_startup_options_test.cc].

Resolves [#8988].

[bazel_startup_options_test.cc]: https://github.com/bazelbuild/bazel/blob/8075057af6108ebc23c146f18eecec911d4b8c00/src/test/cpp/bazel_startup_options_test.cc#L79-L81
[#8988]: https://github.com/bazelbuild/bazel/issues/8988

Testing Done:
- Induced high load on my MBP, then
```console
$ vbazel --local_startup_timeout_secs=1 info release
Starting local Bazel server and connecting to it...
FATAL: couldn't connect to server (16290) after 1 seconds.
```

Closes #11391.

PiperOrigin-RevId: 338729701
diff --git a/src/test/cpp/bazel_startup_options_test.cc b/src/test/cpp/bazel_startup_options_test.cc
index 998bebf..91f1c14 100644
--- a/src/test/cpp/bazel_startup_options_test.cc
+++ b/src/test/cpp/bazel_startup_options_test.cc
@@ -117,6 +117,7 @@
   ExpectIsUnaryOption(options, "install_base");
   ExpectIsUnaryOption(options, "invocation_policy");
   ExpectIsUnaryOption(options, "io_nice_level");
+  ExpectIsUnaryOption(options, "local_startup_timeout_secs");
   ExpectIsUnaryOption(options, "macos_qos_class");
   ExpectIsUnaryOption(options, "max_idle_secs");
   ExpectIsUnaryOption(options, "output_base");