UpdateTestChecks: squelch warning on SCEV output (#67443)

update_analyze_test_checks.py currently outputs a warning when updating
a script with the run line:

  $ opt -passes='print<scalar-evolution>'

saying that the script doesn't support its output, when it indeed does,
as evidenced by several tests in test/Analysis/ScalarEvolution generated
by this script. There is even a test for update_analyze_test_checks that
makes sure that SCEV output is supported. Hence, squelch the warning.

While at it, rename the update_analyze_test_checks test from basic.ll to
a more explicit scev.ll.