Add rockcraft specs for cilium and cilium-operator-generic 1.16.5.

[aznashwan]

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[aznashwan]

There seems to be a known compilation issue in one one of envoy's dependencies (google/cel-cpp) which has been fixed in this PR.

Unfortunately, I was not able to find a sane way to patch in the fix since there's literally 3 layers of build shenanigans going on (cilium/cilium builds cilium/proxy which builds envoyproxy/envoy which depends on that unbuildable google/cel-cpp)

I have tried patching in the envoy commit ID which should include the dependency update with the fix but it unfortunately doesn't seem to work properly.

There's also this cilium/proxy ENVOY_VERSION file with the tag for the envoyproxy/envoy repo tag used in some (but not all!) build stages, but there's yet not a single tag on envoyproxy/envoy which features that fix (it has to be an actual SemVer-format release tag, so we can't just put main there sadly).

At this stage, I do not believe there's anything we could do but wait for:

• envoyproxy/envoy to add that commit with the google/cel-cpp version bump to be pushed to a proper release tag
• cilium/proxy to update their ENVOY_VERSION and bazel build config with the proper tag/commit.