fix(log): WithContext() changed the ctx field of the parent log.Filter

[ionling]

Description (what this PR does / why we need it):

Fix the concurrent problem of log.WithContext() function.

Which issue(s) this PR fixes (resolves / be part of):

Fix #3061

Other special notes for the reviewers:

[shenqidebaozi]

Do we need to determine if f.ctx=ctx when f.ctx=nil? Can we also supplement UT to prove that the modifications have solved the problem and are compatible forward and backward

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1e4e37a) 84.32% compared to head (44795c6) 84.33%.

❗ Current head 44795c6 differs from pull request most recent head cfa9fb8. Consider uploading reports for the commit cfa9fb8 to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3069      +/-   ##
==========================================
+ Coverage   84.32%   84.33%   +0.01%     
==========================================
  Files          88       88              
  Lines        3993     3984       -9     
==========================================
- Hits         3367     3360       -7     
  Misses        449      449              
+ Partials      177      175       -2     

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[ionling]

I have added a UT for this.

About f.ctx=ctx when f.ctx=nil, I think setting a default value is a better solution.
As for backwards compatibility, I think it's a breakable change if there's any code that relies on it.

[shenqidebaozi]

The submitted fix appears to have data race issues

[ionling]

The data race problem was introduced by #2869.
I fixed it using a simpler solution.