Streamline v8 updates and refresh v8 dependency

*Title*: Simplify the process of updating v8 and refresh v8 dependency

*Description*:

While working on Envoy CI update to clang-18 (https://github.com/envoyproxy/envoy/issues/37911), I noticed that v8 dependency is a bit different from the rest and we are not using upstream v8 directly and instead process it somehow, upload it to GCS and use a version from GCS (or something like this, I don't fully understand the process yet). I think that kind of one of the reasons why we haven't updated v8 dependency for a while.

There were at least two things that could improve if we update the version of the v8 dependency:

1. It looks like we can drop one of the external dependencies (https://github.com/envoyproxy/envoy/blob/main/bazel/repository_locations.bzl#L1216-L1230 was merged into the v8 itself)
2. Upstream v8 addressed some of the bugs we hit during migration to clang-18 (here is one example: https://github.com/v8/v8/commit/df459f0e7eda0d1c50698284aab6f424057e076a).

I would like to consider one or both of the following items:

1. Streamline the v8 dependency update process - it would be ideal if we can just consume the upstream repository directly
2. Update v8 depdendency to a newer version.

I'm filing this bug mostly because I'd like to try doing it myself at some point, but haven't had a chance yet to spend time on it.

+cc @phlax