Remove rank, trust, and pruning_score from runtime and chain state

[plind-dm]

These fields were removed from epoch computation but their storage reads, writes, and RPC responses remained. This change completes the removal by returning defaults from all getters, stopping genesis/cleanup writes, and marking storage declarations as deprecated.

Closes #2396

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[plind-dm]

Hi @sam0x17 @gztensor @JohnReedV @camfairchild 👋

Could one of you approve the CI workflows on this PR? Since it's my first contribution from a fork, the 13 workflows are awaiting manual approval.

This PR addresses #2396 — removing rank, trust, and pruning_score from runtime reads/writes. These fields were already removed from epoch computation and wiped by migration, but the codebase still read from storage and returned stale values through RPC. This change completes the cleanup.

Happy to address any feedback. Thanks!