[refactor] Move plugin/sampling/leaderelection to internal/leaderelection

[ary82]

Which problem is this PR solving?

• Towards Remove OTEL/contrib dependency on cmd/collector/app/sampling #6411

Description of the changes

• Move leaderelection package from plugin/sampling/leaderelection to internal/leaderelection

How was this change tested?

• Covered by existing

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: npm run lint and npm run test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.21%. Comparing base (46e7b25) to head (f308811).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6546   +/-   ##
=======================================
  Coverage   96.21%   96.21%           
=======================================
  Files         372      372           
  Lines       21363    21363           
=======================================
  Hits        20554    20554           
  Misses        616      616           
  Partials      193      193           

Flag	Coverage Δ
badger_v1	10.65% <ø> (ø)
badger_v2	2.78% <ø> (ø)
cassandra-4.x-v1-manual	16.55% <ø> (ø)
cassandra-4.x-v2-auto	2.71% <ø> (ø)
cassandra-4.x-v2-manual	2.71% <ø> (ø)
cassandra-5.x-v1-manual	16.55% <ø> (ø)
cassandra-5.x-v2-auto	2.71% <ø> (ø)
cassandra-5.x-v2-manual	2.74% <ø> (+0.02%)	⬆️
elasticsearch-6.x-v1	20.34% <ø> (ø)
elasticsearch-7.x-v1	20.40% <ø> (-0.01%)	⬇️
elasticsearch-8.x-v1	20.56% <ø> (ø)
elasticsearch-8.x-v2	2.77% <ø> (-0.11%)	⬇️
grpc_v1	12.17% <ø> (ø)
grpc_v2	9.04% <ø> (ø)
kafka-3.x-v1	10.33% <ø> (ø)
kafka-3.x-v2	2.78% <ø> (ø)
memory_v2	2.78% <ø> (ø)
opensearch-1.x-v1	20.45% <ø> (-0.01%)	⬇️
opensearch-2.x-v1	20.45% <ø> (-0.01%)	⬇️
opensearch-2.x-v2	2.78% <ø> (+<0.01%)	⬆️
tailsampling-processor	0.51% <ø> (ø)
unittests	95.09% <ø> (ø)

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