[RS4GC] Clamp UseDeoptBundles to true and update tests

The full diff for the test directory may be hard to read because of the
filename clash; so here's all that happened as far as the tests are
concerned:

```
cd test/Transforms/RewriteStatepointsForGC
git rm *ll
git mv deopt-bundles/* ./
rmdir deopt-bundles
find . -name '*.ll' | xargs gsed -i 's/-rs4gc-use-deopt-bundles //g'
```

llvm-svn: 259129