Split client to async and blocking

[ErikBjare]

Rebased and created this PR from #396 hoping that CI will run here

[codecov]

Codecov Report

Patch coverage: 90.24% and project coverage change: +0.08% 🎉

Comparison is base (2dccbf8) 72.07% compared to head (36c86ab) 72.16%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #419      +/-   ##
==========================================
+ Coverage   72.07%   72.16%   +0.08%     
==========================================
  Files          44       45       +1     
  Lines        2815     2831      +16     
==========================================
+ Hits         2029     2043      +14     
- Misses        786      788       +2     

Files Changed	Coverage Δ
aw-sync/src/accessmethod.rs	43.47% <ø> (ø)
aw-sync/src/main.rs	0.00% <ø> (ø)
aw-sync/src/sync.rs	43.29% <ø> (ø)
aw-client-rust/src/blocking.rs	83.33% <83.33%> (ø)
aw-client-rust/src/lib.rs	82.43% <93.10%> (+1.00%)	⬆️

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