autotest (wifi): improve naming of some log files

The network_WiFi_OverlappingBSSScan test runs multiple
hostapd instances, and generates important information
in the hostapd logs. But the names for these log files
are hard to understand ('0' and '1').

Make the test output easier to navigate, by using
descriptive names for the hostapd logs.

Along the way:
- enhance site_linux_router, to allow for descriptive
  log file names
- plumb descriptive log file names up through HostapConfig

While there:
- also use a descriptive name for the pcap
- also use descriptive names in network_WiFi_MultiAuth
- promote a lambda to a class method

BUG=chromium:485194
TEST=network_WiFi_OverlappingBSSScan.obss (new functionality)
TEST=network_WiFi_MultiAuth (new functionality w/simultaneous APs)
TEST=network_WiFi_SimpleConnect.wifi_check11a (regression check)

Change-Id: Ia87a7e28d9d8114b909ea0f8c0f8f50e8eb82a60
Reviewed-on: https://chromium-review.googlesource.com/269776
Trybot-Ready: mukesh agrawal <quiche@chromium.org>
Tested-by: mukesh agrawal <quiche@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: mukesh agrawal <quiche@chromium.org>
4 files changed