chore(gitignore): exclude java code packages from global python env patterns (#13003)

This will be needed for java-bigtable.
Example:
`java-bigtable/google-cloud-bigtable/src/test/java/com/google/cloud/bigtable/test_helpers/env/PrefixGenerator.java`

Author: meltsufin

.gitignore

@@ -40,6 +40,11 @@ ENV/
 env.bak/
 venv.bak/
 
+# Protect Java package folders from global Python virtualenv env/ blanket collisions
+!**/src/main/java/**/env/
+!**/src/test/java/**/env/
+!**/src/main/proto/**/env/
+!**/src/test/proto/**/env/
 
 # Unit test / coverage reports
 .coverage