remove duplicate mocks for the Tracer and the ConnectionTracer

[marten-seemann]

They were introduced to avoid an import loop in the tests in the logging package, but the same can be achieved by having a dedicated package for the tests (logging_test).

This will make work on #3704 easier.

[codecov]

Codecov Report

Merging #4076 (db278fb) into master (d6ac630) will increase coverage by 0.03%.
Report is 2 commits behind head on master.
The diff coverage is 58.54%.

@@            Coverage Diff             @@
##           master    #4076      +/-   ##
==========================================
+ Coverage   83.49%   83.52%   +0.03%     
==========================================
  Files         148      148              
  Lines       15220    15230      +10     
==========================================
+ Hits        12707    12720      +13     
+ Misses       2010     2006       -4     
- Partials      503      504       +1     

Files Changed	Coverage Δ
internal/qtls/go120.go	28.17% <0.00%> (ø)
internal/qtls/go121.go	56.84% <11.11%> (+1.74%)	⬆️
internal/handshake/crypto_setup.go	57.73% <73.33%> (+0.55%)	⬆️
internal/handshake/session_ticket.go	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[marten-seemann]

Merging to avoid further merge conflicts.