Android: Speed up .jar.info file creation in compile_java.py

1. Use the same process rather than forking a new one with multiprocess
2. Apply regular expressions against entire files rather than
   line-by-line.

On my machine, chrome_java .info creation goes from ~1300ms -> ~350ms

Bug: None
Change-Id: I16b8fb6dbcf3ab3d3c262d9c90bfcf562ad05b26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5849686
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1353694}