gh-144418: Increase Android testbed emulator RAM to 4 GB

[mhsmith]

• Fixes Android testbed emulator needs more RAM #144418

[mhsmith]

!buildbot android

[mhsmith]

!buildbot aarch64 Android

[mhsmith]

Testing this has completely broken the aarch64 buildbot in a similar way to #142387, so I've taken it offline until I have a chance to fix it.

[mhsmith]

Specifically, I deleted the existing emulator, and it failed to recreate because it got stuck in a loop of "EGLContext creation failed" crashes. However, the problem isn't specific to this PR; it also happens on the main branch now that the old emulator is gone.

I'll fix this next week, but I don't think it needs to hold up this PR. It works on GitHub Actions, which was its main purpose, and on the x86_64 buildbot. And I've tested it locally on an aarch64 macOS machine, including all of the following cases:

• Emulator doesn't exist
• Emulator exists and its RAM size needs to change
• Emulator exists and its RAM size doesn't need to change

The RAM size can be displayed using the following command:

./android.py test --managed maxVersion -v -- -c 'print([line for line in open("/proc/meminfo") if "MemTotal" in line][0])'