Do not parse operations in dependency

[sdghchj]

Describe the PR
No longer parse operations in dependency, just parse models

Relation issue
#1430

[codecov]

Codecov Report

Base: 85.16% // Head: 85.14% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (d114473) compared to base (c8fad2c).
Patch coverage: 94.44% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1432      +/-   ##
==========================================
- Coverage   85.16%   85.14%   -0.02%     
==========================================
  Files          19       19              
  Lines        3613     3616       +3     
==========================================
+ Hits         3077     3079       +2     
- Misses        458      459       +1     
  Partials       78       78              

Impacted Files	Coverage Δ
types.go	100.00% <ø> (ø)
parser.go	94.45% <90.00%> (-0.11%)	⬇️
golist.go	90.24% <100.00%> (ø)
packages.go	89.12% <100.00%> (+0.03%)	⬆️

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[sdghchj]

After this PR, it is suggested that if you want to parse apis in some external packges，just explicitly include them with flag -d。
swag init -g main.go -d cmd/api,pkg/api