Enable stats v2

[Molter73]

Description

Use Falco's stats v2 to zoom into the events drop metrics and split it into drops due to full buffers vs due to full thread cache.

There was some concern enabling the stats v2 portion of Falco would cause some unwanted procfs scraping from the following functions:

• https://github.com/stackrox/falcosecurity-libs/blob/a283653ee897a17c77d781931170962494188bc3/userspace/libsinsp/metrics_collector.cpp#L241
• https://github.com/stackrox/falcosecurity-libs/blob/a283653ee897a17c77d781931170962494188bc3/userspace/libsinsp/metrics_collector.cpp#L349
• https://github.com/stackrox/falcosecurity-libs/blob/a283653ee897a17c77d781931170962494188bc3/userspace/libsinsp/metrics_collector.cpp#L449

However, after inspecting the code and testing with GDB, it became clear those functions are only called from the snapshot function, so no additional procfs scrapping is added in the way we are using it.

Part of ROX-24691.

Checklist

• Investigated and inspected CI test results
• Updated documentation accordingly

Automated testing

• Added unit tests
• Added integration tests
• Added regression tests

If any of these don't apply, please comment below.

Testing Performed

Since this is a change to metrics, automated testing is not strictly required. As such, changes were tested manually by:

• Running the new image as part of a stackrox deployment.
• Edit the collector daemonset to include the ROX_COLLECTOR_SINSP_THREAD_CACHE_SIZE and the ROX_COLLECTOR_SINSP_BUFFER_SIZE, setting them to low values one at a time.
• Run berserker in a container to add some strain to the system.
• Check the new metrics are working as expected by using curl to query the :8080/ready or :9090/metrics endpoints.

[Stringy]

LGTM!