fix(mongodb): avoid sharded config render helper dependency

[weicao]

Summary

• remove MongoDB sharded config templates' dependency on KB render helper functions for data path and port
• use the same fixed /data/mongodb data root and 27017 port already used by the MongoDB chart/runtime
• child PR for fix(mongodb): avoid rendering null volumes in CmpD templates #2742; does not change the fix(mongodb): avoid rendering null volumes in CmpD templates #2742 owner branch directly

Evidence

• Local worktree based on fix(mongodb): avoid rendering null volumes in CmpD templates #2742 head d33c3033b36c28bed22ab8675d7900a40e796524
• git diff --check PASS
• helm template kb-addon-mongodb addons/mongodb -n kb-system PASS
• Rendered output has no getVolumePathByName / getPortByName / getContainerMemory tokens and no volumes: null
• Target runner focused validation on KB 1.2.0-alpha.1: sharded Cluster reached Running, mongos marker write/read rc=0

Boundary

• Runtime validation used a patched addon chart in mason-idc-mongodb-vc; cleanup exposed a separate KB finalizer cleanup issue, so cleanup is not claimed as normal CLEAN PASS.
• This PR only addresses the config-render helper dependency.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (fix/mongodb-cmpd-volumes-null-kb12@d33c303). Learn more about missing BASE report.

Additional details and impacted files

@@                         Coverage Diff                          @@
##             fix/mongodb-cmpd-volumes-null-kb12   #2747   +/-   ##
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