packaging: add current arch packaging

[zyga]

This patch adds the current snapd packaging for arch as obtained with
the "asp" tool.

Signed-off-by: Zygmunt Krynicki me@zygoon.pl

[codecov-io]

Codecov Report

Merging #3638 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3638      +/-   ##
==========================================
+ Coverage    75.2%   75.21%   +0.01%     
==========================================
  Files         387      387              
  Lines       33452    33452              
==========================================
+ Hits        25157    25162       +5     
+ Misses       6482     6478       -4     
+ Partials     1813     1812       -1

Impacted Files	Coverage Δ
overlord/snapstate/snapstate.go	80.46% <0%> (+0.26%)	⬆️
overlord/ifacestate/helpers.go	63% <0%> (+0.66%)	⬆️

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