Revert "Split vr's generate_jni() target into two"

This reverts commit 345d44c4.

Reason for revert: Suspected cause for build failure.
See https://bugs.chromium.org/p/chromium/issues/detail?id=1394271.

Original change's description:
> Split vr's generate_jni() target into two
>
> This should prevent the default classloader from being cached for the vr
> split, which then causes incorrect values when installing the DFM on T+
> devices.
>
> Bug: b/258453540
> Change-Id: Idd2753aa6fd4539dce9949a5289e99d5c3c90eca
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4062308


> Reviewed-by: Clark DuVall <cduvall@chromium.org>
> Commit-Queue: Andrew Grieve <agrieve@chromium.org>
> Owners-Override: Andrew Grieve <agrieve@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1076505}

Bug: b/258453540
Change-Id: I7bd15bd8309ef96551991c368565bf4891ad1ef3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4059951
Auto-Submit: Hailey Wang <haileywang@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Hailey Wang <haileywang@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1076571}