interfaces/misc: updates for unity7/x11 (LP: #1663221), browser-support, network-control (LP: #1679295) and mount-observe

[jdstrand]

• interfaces/unity7,x11: update for NETLINK_KOBJECT_UEVENT (LP: #1663221)
• interfaces/browser-support: update sysfs reads for newer browser versions
• interfaces/network-control: rw for ieee80211 advanced wireless (LP: #1679295)
• interfaces/mount-observe: allow read on sysfs entries for block devices

[zyga]

LGTM

CC @mvo5 - we need a new 2.27

[codecov-io]

Codecov Report

Merging #3715 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3715      +/-   ##
==========================================
+ Coverage   75.65%   75.67%   +0.01%     
==========================================
  Files         391      391              
  Lines       33849    33849              
==========================================
+ Hits        25609    25614       +5     
+ Misses       6418     6414       -4     
+ Partials     1822     1821       -1

Impacted Files	Coverage Δ
interfaces/builtin/network_control.go	100% <ø> (ø)	⬆️
interfaces/builtin/unity7.go	67.85% <ø> (ø)	⬆️
interfaces/builtin/x11.go	100% <ø> (ø)	⬆️
interfaces/builtin/browser_support.go	76.31% <ø> (ø)	⬆️
interfaces/builtin/mount_observe.go	100% <ø> (ø)	⬆️
overlord/snapstate/snapstate.go	80.72% <0%> (+0.26%)	⬆️
overlord/ifacestate/helpers.go	63% <0%> (+0.66%)	⬆️

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