feat: Add redis connection metrics (close #127)

[GGXXLL]

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[codecov]

Codecov Report

Merging #128 (961081d) into master (37893d4) will increase coverage by 0.71%.
The diff coverage is 97.97%.

@@            Coverage Diff             @@
##           master     #128      +/-   ##
==========================================
+ Coverage   76.77%   77.49%   +0.71%     
==========================================
  Files          83       85       +2     
  Lines        3143     3239      +96     
==========================================
+ Hits         2413     2510      +97     
+ Misses        542      540       -2     
- Partials      188      189       +1     

Impacted Files	Coverage Δ
c.go	76.71% <ø> (ø)
otredis/module.go	91.30% <91.30%> (ø)
observability/metrics.go	100.00% <100.00%> (ø)
observability/observability.go	100.00% <100.00%> (ø)
otredis/metrics.go	100.00% <100.00%> (ø)
otredis/provider.go	78.82% <100.00%> (+2.82%)	⬆️
dtx/sagas/mysqlstore/mysql_store.go	87.34% <0.00%> (+3.79%)	⬆️

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