improvement(upgrade): allow to skip truncate checks in upgrade tests

[vponomaryov]

Those checks may be done on cheap upgrade setups.
And those checks may timeout on huge expensive setups.
Also, it will take additional time on expensive setups.

So, add possibility to skip truncate checks for such cases.

Testing

• scylla-staging/valerii/vp-rolling-upgrade-custom-d2-w1-latency-regression-v2#4

PR pre-checks (self review)

• I added the relevant backport labels
• I didn't leave commented-out/debugging code

Reminders

• Add New configuration option and document them (in sdcm/sct_config.py)
• Add unit tests to cover my changes (under unit-test/ folder)
• Update the Readme/doc folder relevant to this change (if needed)

[vponomaryov]

Implemented based on the needs of the following task:

• https://github.com/scylladb/qa-tasks/issues/1943