simpleperf: Improve log message

When truncating stack data in samples, use "truncate"
instead of "cut", to make it easier to understand.

Bug: 297776904
Test: run simpleperf manually
Test: simpleperf_unit_test
Change-Id: Ide7496a84b6cf1be57a5f0d7d2a440addaef3b6c
7 files changed