Java arm64 images, buster variants for back compat

[Chuxel]

As described in #558 (comment), the situation for Docker on M1 macs is not ideal since both debian:buster nor ubuntu:focal experience segmentation faults due to an issue in libss1.1. It seems unlikely that buster will be patched now that bullseye is out (and buster therefore gets security fixes only).

Therefore this PR:

1. Adds arm64 builds for Debian bullseye
2. Adds buster variants that are x86 only for backwards compat.
3. Keeps the default image tags (8, 11, 16) at buster

@testforstephen @akaroml - Debian bullseye is pretty recent, but works on arm64. Would it make sense to default to stick with buster as is done here? Java should be fairly abstracted from OS version updates, but I didn't want to make an update that could break users. Thoughts?

//cc: @joshspicer @2percentsilk @bamurtaugh @chrmarti

[testforstephen]

Looks good to me. Only one concern is how user can easily distinguish which Java variant to use when they use "Remote-Containers: Add Remote Development Configuration Files..." command to pick up a Java definition?

This is current dropdown for Java versions:

I assume the PR will add two more options like "11-bullseye" and "16-bullseye". Is it possible to show some details for these options to mention the architecture they support?

[Chuxel]

@testforstephen Yeah the list would include both buster and bullseye. I could have the label ("Java version") mention that bullseye should be used for arm64 and M1 macs.

I assume you think it makes sense to stick with buster by default?

[testforstephen]

yes, since bullseye is very new and we can stay on buster as default for a while. But eventually we need to switch to bullseye at some point in future.