feat: add default api for xlog

[sysulq]

Describe what this PR does / why we need it

Does this pull request fix one issue?

Describe how you did it

Describe how to verify it

Special notes for reviews

[codecov-commenter]

Codecov Report

Merging #382 (9b4e731) into master (771ae2a) will decrease coverage by 0.02%.
The diff coverage is 4.00%.

@@            Coverage Diff             @@
##           master     #382      +/-   ##
==========================================
- Coverage   40.06%   40.03%   -0.03%     
==========================================
  Files          84       84              
  Lines        5551     5590      +39     
==========================================
+ Hits         2224     2238      +14     
- Misses       3169     3194      +25     
  Partials      158      158              

Impacted Files	Coverage Δ
pkg/xlog/config.go	18.64% <0.00%> (-1.00%)	⬇️
pkg/xlog/field.go	0.00% <0.00%> (ø)
pkg/xlog/log.go	72.05% <ø> (ø)
pkg/xlog/api.go	16.66% <9.09%> (-83.34%)	⬇️
pkg/client/redis/config.go	33.33% <0.00%> (-0.54%)	⬇️
pkg/client/grpc/balancer/p2c/least_loaded.go	87.50% <0.00%> (+12.50%)	⬆️
pkg/store/gorm/logger.go	37.50% <0.00%> (+22.91%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.