roachtest: Update more roachtests to use encryption-at-rest on some random runs

[itsbilal]

Currently, the only roachtests that run with encryption-at-rest enabled are:

1. All the kv{0,95}/enc=true/* tests
2. Half of all clearrange/checks={false,true} runs (since roachtest: Use encryption-at-rest in some random clearrange runs #57086).
3. All of engine/switch/encrypted/nodes=*
4. All of encryption/nodes=1

To aid in detecting any issues concerning interactions with encryption-at-rest, we should be running a wider variety of roachtests with encryption-at-rest enabled. This could be implemented using a random boolean at cluster start time, similar to how it's done for clearrange, as that would avoid doubling the number of roachtests we run.

[blathers-crl]

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