Refactor/tokens events

[syan095]

Added events so all operations with balance changes deposit events
Added unit test to ensure these events are emitted

Fixes #726

[codecov-commenter]

Codecov Report

Merging #729 (18d8eb3) into master (2b5d4ce) will increase coverage by 0.39%.
The diff coverage is 92.89%.

@@            Coverage Diff             @@
##           master     #729      +/-   ##
==========================================
+ Coverage   75.21%   75.61%   +0.39%     
==========================================
  Files          84       84              
  Lines        7643     7766     +123     
==========================================
+ Hits         5749     5872     +123     
  Misses       1894     1894              

Impacted Files	Coverage Δ
currencies/src/mock.rs	94.73% <ø> (ø)
tokens/src/mock.rs	31.14% <ø> (ø)
currencies/src/lib.rs	50.99% <81.81%> (-5.29%)	⬇️
tokens/src/lib.rs	85.54% <86.31%> (+0.92%)	⬆️
currencies/src/tests.rs	100.00% <100.00%> (ø)
tokens/src/tests.rs	99.84% <100.00%> (+0.01%)	⬆️
nft/src/mock.rs	100.00% <0.00%> (ø)
oracle/src/mock.rs	100.00% <0.00%> (ø)
auction/src/mock.rs	100.00% <0.00%> (ø)
... and 11 more

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