autotest: Move WiFi capability parsing into LinuxSystem

Move capability parsing into LinuxSystem close to the datastructures it
makes use of.  Move the tracking of capabilities out of site_wifitest
and into the objects representing the systems with the capabilities.

TEST=network_WiFiMatFunc/012CheckMaskedBSSID still passes.  This test
uses the multi-ap capability.
BUG=chromium:230660

Change-Id: I794ecc953be208c361b9e65cdc807742b1e3da6b
Reviewed-on: https://gerrit.chromium.org/gerrit/50242
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
3 files changed