Add dump state for wificond interface classes

Add dump state for wificond interface classes

This allows wificond's ClientInterfaceImpl and
ApInterfaceImpl to dump state.

The dump state includes scan capabilities, wiphy features, and
number of current associated stations for AP mode.

This also adds the missing const keyword for IsAssociated().

Bug: 31336376
Test: compile, manual test

Sample dump output:
Current wiphy index: 0
Cached interfaces list from kernel message:
Interface index: 23, name: p2p0, mac address: 66:bc:0c:47:df:00
Interface index: 22, name: wlan0, mac address: 64:bc:0c:47:df:00
------- Dump of client interface with index: 22 and name: wlan0-------
Max number of ssids for single shot scan: 10
Max number of ssids for scheduled scan: 16
Max number of match sets for scheduled scan: 16
Device supports random MAC for single shot scan: 1
Device supports random MAC for scheduled scan: 1
------- Dump End -------
--------- 0.004s was the duration of dumpsys wificond

Change-Id: I862974af743ca6ca303dfc1a4f6c773dd5b7a03e