Support upgrading version in bzlmod single_version_override

[rarkins]

Discussed in #32446

^{Originally posted by honnix November 11, 2024}

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#22610 added the feature supporting single_version_override, however there is no way to allow renovate to update version specified in single_version_override. While it is understandable users might intend to pin that version, in practice it is not always true. For example, when patching MODULE.bazel itself, it is often necessary to specify a version in single_version_override, but it does not necessarily mean users don't want to get version bump, as long as a new version doesn't invalidate the patch file (if it does bazel would fail immediately anyway).

I think it makes sense to add a config to enable version bump in this case.

Reproduction: https://github.com/renovate-reproductions/32446