add cache_write metric definition

Add Cobalt definition for the cache_write metric for FTS.

Bug: 44243
Test: fx build
Change-Id: I7a7dc2ac2fd6a603b0ca45691ffeb7e650422fc7
1 file changed
tree: 647cdc0ac942ec341b87460f4a7b8f0799c10fd8
  1. cobalt_internal/
  2. fuchsia/
  3. .gitignore
  4. BUILD.gn
  5. check.py
  6. OWNERS
  7. projects.yaml