Cilium looks if CILIUM_FEATURE_METRICS_WITH_DEFAULTS is set in the
local environment to determine if it should include default metric
values, which is useful for testing and generating documentation. The
was introduced in commit [0]  and is not intended to be used in
production scenarios.

The metrics package also includes host-specific version information,
such as Kubernetes and Linux kernel version information. This info
should not appear in published documents, and will cuses issues if we
want to automatically detect out-of-sync documents in CI.

We introduces a similar environment-based mechanism to hide host-
specific info such as that noted above. If the new variable
CILIUM_FEATURE_METRICS_WITHOUT_HOST_INFO is set in the local env,
both the agent and the operator will disable version-specific metrics.
The source of these metrics is also updated to only populate them if
the metric is enabled.

Rationale for a new variable was to avoid overloading of the existing
variable, while following the existing precedent for modifying the
behaviour of metrics for development purposes. This also means existing
test mechanisms are unaffected.

[0] 18fcd45 ("pkg/metrics: do not enable all metric defaults")

Signed-off-by: Alasdair McWilliam <alasdair.mcwilliam@isovalent.com>

Fix the smoke test workflow to fail correctly if feature metric docs
are out of sync.

This has required the workflow to set the new environment variable
CILIUM_FEATURE_METRICS_WITHOUT_HOST_INFO when installing, to avoid CI
runner version information being added to the generated documentation
that is then used to compare diffs with. Otherwise this will always
cause failures.

The variable is passed in extraEnv[3] to avoid conflicts with other
environment variables passed in actions/set-env-variables.

Fixes: eabba03 ("docs: document feature metrics and add rst generator")
Signed-off-by: Alasdair McWilliam <alasdair.mcwilliam@isovalent.com>

Signed-off-by: Alasdair McWilliam <alasdair.mcwilliam@isovalent.com>