Wait briefly before starting to poll the emulator in android-emulator-tests.sh

[marcprux]

While waiting for the Android emulator to start up, we poll it with adb wait-for-any-device. This seems to crash sometimes (e.g, in this workflow run for apple/swift-configuration#140) with:

USER_INFO    | Emulator is performing a full startup. This may take upto two minutes, or more.
WARNING      | Failed to process .ini file /home/runner/.android/emu-update-last-check.ini for reading.
timeout: the monitored command dumped core
/home/runner/work/swift-configuration/swift-configuration/github-workflows/.github/workflows/scripts/android/android-emulator-tests.sh: line 99:  6236 Aborted                 timeout "${ANDROID_EMULATOR_TIMEOUT}" adb wait-for-any-device
WARNING      | Failed to process .ini file /home/runner/.android/emu-update-last-check.ini for reading.

This PR introduces a short delay between launching the emulator and starting the polling on the theory that the emulator startup process is conflicting with the adb command.

CC: @finagolfin

[marcprux]

Oops, this might conflict with the delay introduced in #221. Converting to draft while I inquire…