Use MsgOut.UnsendableReason instead of checking contact status

[rowanseymour]

Which might be different to what it was when the message was actually sent, e.g. a send message action and then a update status action

[codecov]

Codecov Report

Merging #657 (29e82a4) into main (acd61cf) will decrease coverage by 0.03%.
The diff coverage is 54.54%.

@@            Coverage Diff             @@
##             main     #657      +/-   ##
==========================================
- Coverage   62.20%   62.17%   -0.04%     
==========================================
  Files         132      132              
  Lines       12894    12895       +1     
==========================================
- Hits         8021     8017       -4     
- Misses       4014     4017       +3     
- Partials      859      861       +2     

Impacted Files	Coverage Δ
core/models/msgs.go	56.56% <54.54%> (-0.64%)	⬇️

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