Add test coverage for data replication layer

[kelvinmwinuka]

This change adds test cases for the raft and memberlist data replication logic.

[codecov]

Codecov Report

Attention: Patch coverage is 75.73840% with 115 lines in your changes are missing coverage. Please review.

Project coverage is 75.76%. Comparing base (7e585dc) to head (0108444).

Files	Patch %	Lines
echovault/keyspace.go	50.44%	52 Missing and 4 partials ⚠️
internal/modules/list/commands.go	78.57%	0 Missing and 12 partials ⚠️
internal/modules/sorted_set/commands.go	89.58%	0 Missing and 10 partials ⚠️
echovault/echovault.go	50.00%	8 Missing and 1 partial ⚠️
internal/modules/set/commands.go	86.15%	0 Missing and 9 partials ⚠️
internal/modules/hash/commands.go	82.50%	0 Missing and 7 partials ⚠️
internal/modules/generic/commands.go	86.84%	1 Missing and 4 partials ⚠️
internal/modules/string/commands.go	75.00%	0 Missing and 3 partials ⚠️
echovault/modules.go	83.33%	1 Missing and 1 partial ⚠️
echovault/test_helpers.go	66.66%	0 Missing and 1 partial ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #43      +/-   ##
==========================================
+ Coverage   74.76%   75.76%   +1.00%     
==========================================
  Files          46       46              
  Lines        8210     7796     -414     
==========================================
- Hits         6138     5907     -231     
+ Misses       1623     1467     -156     
+ Partials      449      422      -27     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.