release-26.2: kvserver: deflake TestCrashWhileTruncatingSideloadedEntries

[blathers-crl]

Backport 1/1 commits from #170631 on behalf of @pav-kv.

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The test manually emulated a crash by tripping circuit breakers on the follower's dialer, taking a CrashClone, and stopping the server.

However, circuit breakers only block the follower's outgoing traffic — the leader can still send messages to the follower via the leader's own connection/stream. This caused a flake where the follower received and acknowledged a raft entry that wasn't synced to disk before CrashClone, leading to a panic on restart.

Replace the manual crash emulation with the canonical tc.CrashNode(), which uses rpc.Partitioner to add bidirectional partitions before taking the crash snapshot, blocking all traffic.

Informs #170454
Fixes #117785

Epic: none
Release note: None

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Release justification: test deflake

[trunk-io]

😎 Merged directly without going through the merge queue, as the queue was empty and the PR was up to date with the target branch - details.

[blathers-crl]

Thanks for opening a backport.

Before merging, please confirm that the change does not break backwards compatibility and otherwise complies with the backport policy. Include a brief release justification in the PR description explaining why the backport is appropriate. All backports must be reviewed by the TL for the owning area. While the stricter LTS policy does not yet apply, please exercise judgment and consider gating non-critical changes behind a disabled-by-default feature flag when appropriate.

[cockroach-teamcity]

This change is 

[pav-kv]

Holding off the merge since there is some race in maybe_stressrace to fix first.

[pav-kv]

CI should be fixed after #170893