Add the wiredtiger-perf-btree tests in evergreen.yml.
The btree tests are as follows:
- small-btree
- small-btree-backup
- medium-btree
- medium-btree-backup
- parallel-pop-btree
- update-only-btree
- update-btree
- update-large-record-btree
- modify-large-record-btree
- modify-force-update-large-record-btree