chore: fix synth.py error and enable multiple autosynth commits (#215)

Author: chingor13

synth.py

@@ -14,7 +14,9 @@
 
 """This script is used to synthesize generated parts of this library."""
 
-import synthtool.languages.java
+import synthtool.languages.java as java
+
+AUTOSYNTH_MULTIPLE_COMMITS = True
 
 java.common_templates(excludes=[
   'README.md',