Add long idle tests for key_idle_power_cases
Add long idle tests for key_idle_power_cases

There are several key tasks/behaviors that are currently not covered by
key_idle_power cases, e.g., tasks suspended by the PowerMonitor. Add
two additional tests with longer (90 second) idle durations to capture
such behavior.

BUG=466213

Review URL: https://codereview.chromium.org/1243703002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#344318}

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