fix: no copy some fields at ResponseHeader and RequestHeader

[wzekin]

What type of PR is this?

fix

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• 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.
• Attach the PR updating the user documentation if the current PR requires user awareness at the usage level. User docs repo.

(Optional) Translate the PR title into Chinese.

修复 ResponseHeader 和 RequestHeader 的 CopyTo 方法没有复制部分字段的问题

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

en:

• In ResponseHeader.CopyTo, the protocol and headerLength fields are not copied
• In RequestHeader.CopyTo, the protocol field is not copied

zh(optional):

• 在 ResponseHeader.CopyTo 中， 没有复制protocol和headerLength字段
• 在 RequestHeader.CopyTo 中， 没有复制protocol字段

(Optional) Which issue(s) this PR fixes:

(Optional) The PR that updates user documentation:

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.18 🎉

Comparison is base (ca1fb0e) 75.59% compared to head (c6d3ddc) 75.78%.

❗ Current head c6d3ddc differs from pull request most recent head 3e262fa. Consider uploading reports for the commit 3e262fa to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #796      +/-   ##
===========================================
+ Coverage    75.59%   75.78%   +0.18%     
===========================================
  Files           97       97              
  Lines         9477     9480       +3     
===========================================
+ Hits          7164     7184      +20     
+ Misses        1862     1846      -16     
+ Partials       451      450       -1     

Impacted Files	Coverage Δ
pkg/protocol/header.go	78.08% <100.00%> (+1.16%)	⬆️

... and 1 file with indirect coverage changes

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[welkeyever]

LGTM