Update bot may downgrade current stack version

[antoineco]

The update bot recently updated the stack from 8.15 to 8.16, then downgraded it to 8.15 again at a later time¹:

1. f3c81fd
2. 8e62bd4

This can happen because we pick the latest (GitHub) release by creation date that matches the major semver, then apply it blindly if it differs from the current stack version.

In this particular situation, Elastic created a patch release for 8.15 after the last patch release for 8.16, which led to this downgrade.

Although these situations seem exceptional, we should not only validate that the release satisfies the semver, but also that it is greater than the current stack version.

Footnotes

1. with another 8.16 patch in between, but that's irrelevant for this issue. ↩