Add fxevent.Decorated and emit it from fx.Decorate

[sywhang]

This adds Decorated event to fx/fxevent package. Similar to Provided, this emits information on the following:

• The name of the decorator
• The dependencies of the decorator
• Types being decorated by the decorator

fx.Decorate now emits this event upon decoration.

This also needs to fix Dig to the latest master to include the dig.FillDecorateInfo API.

Ref: GO-1208

[codecov]

Codecov Report

Merging #843 (695650f) into master (66a9373) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #843      +/-   ##
==========================================
+ Coverage   98.42%   98.45%   +0.03%     
==========================================
  Files          30       30              
  Lines        1076     1098      +22     
==========================================
+ Hits         1059     1081      +22     
  Misses         11       11              
  Partials        6        6              

Impacted Files	Coverage Δ
fxevent/console.go	100.00% <100.00%> (ø)
fxevent/event.go	100.00% <100.00%> (ø)
fxevent/zap.go	100.00% <100.00%> (ø)
module.go	100.00% <100.00%> (ø)

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