[ISSUE #473] support nsresolver in TraceConfig

[dbl-x]

What is the purpose of the change

support ns-resolver config in TraceConfig

close #473

[ShannonDing]

it is better to add a new nameserver resolver for trace config, but for old users, it is better to keep the "WithNameServer" at the same time and do create a default resolver inner for it.

[codecov-io]

Codecov Report

Merging #474 into master will decrease coverage by 0.03%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #474      +/-   ##
==========================================
- Coverage   24.80%   24.77%   -0.04%     
==========================================
  Files          49       49              
  Lines        5716     5723       +7     
==========================================
  Hits         1418     1418              
- Misses       4095     4102       +7     
  Partials      203      203              

Impacted Files	Coverage Δ
internal/trace.go	27.05% <0.00%> (-0.67%)	⬇️

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[dbl-x]

it is better to add a new nameserver resolver for trace config, but for old users, it is better to keep the "WithNameServer" at the same time and do create a default resolver inner for it.

Great suggestion, already done this