change: remove backslash before slash when encoding

[Lewisyixin]

Description

Remove backslash before slash when setting routes to etcd or generating log to local files.
The backslash is from lua-cjson and it can be turned off by default.
https://github.com/openresty/lua-cjson/#encode_escape_forward_slash

Fixes (#7785)
Fixes (#7606)

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[moonming]

Is this a break change？

[Lewisyixin]

Exactly, I can't guarantee it. The first time I encountered this kind of problem is when dealing with data in etcd((#7606)) . Then I found it was caused by lua-json and avoid it by turning off json.encode_escape_forward_slash in my own plugin next time.
When I found other people meeting the same problem in #7785 I helped them by json.encode_escape_forward_slash and asked spacewander if this param can be default turned off in apisix.core.json to avoid backslash before slash when json encoding. He let me to try to submit a PR.
I learned this param from https://github.com/openresty/lua-cjson/#encode_escape_forward_slash and used it in my plugin for some months. But determining whether it will affect other components in apisix is maybe beyond my ability.

[spacewander]

Could you add a test like

apisix/t/core/json.t

Line 132 in cffa4b6

=== TEST 6: decode/encode empty array

?

[spacewander]

There are some broken tests:
https://github.com/apache/apisix/runs/8062783800?check_suite_focus=true
https://github.com/apache/apisix/runs/8062783743?check_suite_focus=true

I have checked them and all of them are about extra \ before / in the expected string.

Would you please update the test cases?

[tzssangglass]

Is this a break change？

Yes, because the format of the json parsing has changed.

[github-actions]

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[github-actions]

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