More UserInterfaceSystem metrics

[redmushie]

Description

Adds metrics to UserInterfaceSystem Update and SetState methods:

• robust_bui_update_usage is the Update step broken down into 3 sub-phases with timing per phase.
• robust_bui_set_state_usage is the SetState method per BUI state object type
• robust_bui_range_check_usage is the parallel range check job from the Update method, per BUI enum key.

Adds CVar to enable these metrics:

• metrics.granular_ui_system, default false.

Here's hoping this gives us enough info to find where our precious CPU time is going.

Reason

We're getting lag reports from users, and seeing this huge uptick in the UserInterfaceSystem update usage:

https://grafana.starlight.network/d/qyFqpFiGk2/perf-metrics?orgId=1&from=2026-07-01T08:08:45.015Z&to=2026-07-01T10:08:31.539Z&timezone=browser&var-Server=watchdog-starlight%2Fbeta-watchdog&viewPanel=panel-100

Some shifts it doesn't happen, some it's present almost the entire round (as shown here).

I've not been able to determine what UI causes this, hence more granular metrics for the SharedUserInterfaceSystem.

Please squash merge

[redmushie]

Examples of resulting metrics.

robust_bui_range_check_usage_sum

Query rate(robust_bui_range_check_usage_sum[30s]), Legend {{bui}}

robust_bui_set_state_usage_sum

Query rate(robust_bui_set_state_usage_sum[30s]), Legend {{bui}}

robust_bui_update_usage_sum

Query rate(robust_bui_update_usage_sum[30s]), Legend {{phase}}