feat(form): add array collection format in form binding

[slowhigh]

Enables the possibility of collecting array data from queries or form data by specifying the collection_format tag in structs.

Several people are waiting for this feature to be updated.

cc @Simon-Saaw

Related PR: #2750
Close #2750

[takanuva15]

Just saw the old PR you linked and was excited to see that someone else took up the old dead PR to make this a feature in gin. Looking forward to getting this merged!

[slowhigh]

Thank you for your comments. @takanuva15

[appleboy]

@slowhigh Any updates?

[slowhigh]

@appleboy Thank you. Good idea.

[appleboy]

@slowhigh Lint error https://github.com/gin-gonic/gin/actions/runs/10399149908/job/28847599766?pr=3986

[slowhigh]

@appleboy I have addressed the lint error you mentioned.

[appleboy]

@slowhigh LGTM

[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 6 lines in your changes missing coverage. Please review.

Project coverage is 98.85%. Comparing base (3dc1cd6) to head (70108c0).
Report is 68 commits behind head on master.

Files	Patch %	Lines
binding/form_mapping.go	77.77%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3986      +/-   ##
==========================================
- Coverage   99.21%   98.85%   -0.36%     
==========================================
  Files          42       44       +2     
  Lines        3182     2799     -383     
==========================================
- Hits         3157     2767     -390     
- Misses         17       19       +2     
- Partials        8       13       +5     

Flag	Coverage Δ
	?
-tags "sonic avx"	98.84% <77.77%> (?)
-tags go_json	98.84% <77.77%> (?)
-tags nomsgpack	98.83% <77.77%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	98.85% <77.77%> (-0.36%)	⬇️
go-1.22	98.85% <77.77%> (?)
macos-latest	98.85% <77.77%> (-0.36%)	⬇️
ubuntu-latest	98.85% <77.77%> (-0.36%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.