Add a write barrier elimination pass

We can eliminate redundant write barriers as we don't need several
for the same receiver. For example:

```
MyObject o;
o.inner_obj = io;
o.inner_obj2 = io2;
o.inner_obj3 = io3;
```

We can keep the write barrier for `inner_obj` and remove the other
two.

Note that we cannot perform this optimization across
invokes, suspend check, or instructions that can throw.

Local improvements (pixel 5, speed compile):
 * System server: -280KB (-0.56%)
 * SystemUIGoogle: -330KB (-1.16%)
 * AGSA: -3876KB (-1.19%)

Bug: 260843353
Fixes: 260843353
Change-Id: Ibf98efbe891ee00e46125853c3e97ae30aa3ff30

0 files changed, 0 insertions, 0 deletions