feat: add Cookies function to return all the request cookies

[justlorain]

What type of PR is this?

feat

Check the PR title.

• This PR title match the format: <type>(optional scope): <description>
• The description of this PR title is user-oriented and clear enough for others to understand.

(Optional) Translate the PR title into Chinese.

添加 Cookies 方法

(Optional) More detail description for this PR(en: English/zh: Chinese).

en: Cookies returns all the request cookies
zh(optional): Cookies 返回所有的请求 Cookie

Which issue(s) this PR fixes:

null

[codecov]

Codecov Report

Base: 69.34% // Head: 69.65% // Increases project coverage by +0.31% 🎉

Coverage data is based on head (8d3dfca) compared to base (81332e6).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 8d3dfca differs from pull request most recent head 48f752b. Consider uploading reports for the commit 48f752b to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #495      +/-   ##
===========================================
+ Coverage    69.34%   69.65%   +0.31%     
===========================================
  Files           93       93              
  Lines         8874     8843      -31     
===========================================
+ Hits          6154     6160       +6     
+ Misses        2355     2319      -36     
+ Partials       365      364       -1     

Impacted Files	Coverage Δ
pkg/protocol/header.go	75.59% <100.00%> (+0.65%)	⬆️
pkg/common/adaptor/request.go	80.00% <0.00%> (-0.96%)	⬇️
pkg/common/config/option.go	100.00% <0.00%> (ø)
pkg/common/errors/errors.go	87.95% <0.00%> (ø)
pkg/network/netpoll/transport.go	0.00% <0.00%> (ø)
pkg/protocol/cookie.go	88.47% <0.00%> (+2.05%)	⬆️
pkg/route/engine.go	63.19% <0.00%> (+2.64%)	⬆️
pkg/app/server/option.go	98.55% <0.00%> (+2.77%)	⬆️

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[FGYFFFF]

Can the title be more detailed?

[welkeyever]

LGTM, thx~