fix openapi item with url illegalKey 400 error

[AbnerHuang2]

What's the purpose of this PR

fix openapi item with url illegalKey 400 error

Which issue(s) this PR fixes:

Fixes #4447

Brief changelog

get/update/delete the item key with / \ or start with . will encode key by encodeItems API, otherwise, it will act like old way.

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[codecov-commenter]

Codecov Report

Merging #4549 (f5f397b) into master (70791c8) will decrease coverage by 0.01%.
The diff coverage is 39.13%.

@@             Coverage Diff              @@
##             master    #4549      +/-   ##
============================================
- Coverage     53.31%   53.29%   -0.02%     
- Complexity     2707     2710       +3     
============================================
  Files           494      495       +1     
  Lines         15416    15438      +22     
  Branches       1599     1599              
============================================
+ Hits           8219     8228       +9     
- Misses         6637     6651      +14     
+ Partials        560      559       -1     

Impacted Files	Coverage Δ
...apollo/adminservice/controller/ItemController.java	7.14% <0.00%> (-0.15%)	⬇️
...k/apollo/openapi/v1/controller/ItemController.java	12.19% <0.00%> (-2.96%)	⬇️
...p/framework/apollo/portal/api/AdminServiceAPI.java	12.95% <0.00%> (-0.14%)	⬇️
...p/framework/apollo/portal/service/ItemService.java	46.32% <0.00%> (-0.53%)	⬇️
.../apollo/openapi/client/url/OpenApiPathBuilder.java	96.49% <100.00%> (+0.19%)	⬆️
...ctrip/framework/apollo/openapi/utils/UrlUtils.java	100.00% <100.00%> (ø)
...work/apollo/biz/message/DatabaseMessageSender.java	56.25% <0.00%> (-8.34%)	⬇️
...ework/apollo/internals/RemoteConfigRepository.java	88.34% <0.00%> (+3.06%)	⬆️

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[nobodyiam]

LGTM