Add progress feature to -Oz inlining policy.

compiler_opt/rl/inlining/config.py

diff --git a/compiler_opt/rl/inlining/config.py b/compiler_opt/rl/inlining/config.py
index aae614d..c84ae67 100644
--- a/compiler_opt/rl/inlining/config.py
+++ b/compiler_opt/rl/inlining/config.py
@@ -41,6 +41,7 @@
           'edge_count',
           'callsite_height',
           'cost_estimate',
+          'progress',
 
           # Expanded cost features
           'sroa_savings',