Upgrade the global gitignore files with some more files to ignore (so…

…nic-net#18317)

* Upgrade the global gitignore files with some more files to ignore

Specifically, ignore the Dockerfile.cleanup files that are autogenerated
for the docker containers, and ignore the udeb files built as part of
openssh.

There are a lot more files that should be ignored, but this is taking
care of the easy ones.

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

.gitignore

@@ -12,6 +12,7 @@ fsroot/
 fs.*
 target/
 *.deb
+*.udeb
 *.changes
 *.buildinfo
 *.tar
@@ -28,8 +29,13 @@ sonic-slave*/*.log
 # Autogenerated Dockerfiles
 sonic-slave*/Dockerfile
 sonic-slave*/Dockerfile.user
+sonic-slave*/Dockerfile.cleanup
 dockers/*/Dockerfile
+dockers/*/Dockerfile.cleanup
+dockers/*/Dockerfile-dbg.cleanup
 platform/*/docker-*/Dockerfile
+platform/*/docker-*/Dockerfile.cleanup
+platform/*/docker-*/Dockerfile-dbg.cleanup
 
 # Autogenerated manifest files
 dockers/*/*manifest*