Revert "disable bpfloader selinux_context support"

This reverts commit 8e5e239dd0a7856e486a9e2d772ef3a9e38021eb.

No longer required now that selinux change has landed.

(while we're at it bump the bpfloader version to v0.19 just
 to make sure we can tell these apart in the future)

This is a cherrypick to tm-dev of reviewed/approved but unsubmitted:
  https://android-review.googlesource.com/c/platform/system/bpf/+/2132534

Ignore-AOSP-First: will be cherrypicked to aosp master

Bug: 218408035
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I0b3349ef908bbfd225b8b7f83b2a4a8870c1e409