kvserver/liveness: liveness storage sends batch requests without admission header

[stevendanna]

Describe the problem

At least one source of the reports found in #112680 is likely the following to uses of the Get and Scan methods onkv.DB in liveness.Storage:

cockroach/pkg/kv/kvserver/liveness/storage.go

Line 73 in a1cfb1b

record, err := ls.db.Get(ctx, keys.NodeLivenessKey(nodeID))

cockroach/pkg/kv/kvserver/liveness/storage.go

Line 201 in a1cfb1b

kvs, err := ls.db.Scan(ctx, keys.NodeLivenessPrefix, keys.NodeLivenessKeyMax, 0)

Replacing these two uses a db.Txn() avoids the warning in a good number of the reproductions I've seen locally. We likely don't want a Txn here though, so we'll want to use a different API that allows us to pass in an admission header.

Jira issue: CRDB-41842

[blathers-crl]

Hi @stevendanna, please add branch-* labels to identify which branch(es) this C-bug affects.

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[aadityasondhi]

Thanks for reporting this and finding the source!