Add support for reading `net/data/ssl/certificates` files

* After supporting netty, the certificates files are needed to start up the HTTP server. Those files must be moved to the emulator which happens through the changes in AndroidTest.xml, isolated-storage
has been disabled to allow the emulator to access the storage freely without restriction. Otherwise
I will have to change the destination of the data files which will result in divergence.

* Added the newly introduced test utility java classes including netty to the `jarjar_excludes` as they must not be jarjared because they are not part of the bootclasspath.

Test: atest NetHttpTests
Bug: 319629150
Bug: 304217500
Change-Id: I2331873a9e178783319f889a377ba7e390ecdd6f