perf-test: rename memory tests

The common suffix will help running them all automatically.

diff --git a/performance-test/M00-new b/performance-test/M00-new.sh
similarity index 100%
rename from performance-test/M00-new
rename to performance-test/M00-new.sh

diff --git a/performance-test/M01-dump-restore b/performance-test/M01-dump-restore.sh
similarity index 100%
rename from performance-test/M01-dump-restore
rename to performance-test/M01-dump-restore.sh