Update bluetooth-test-util-lib to modern standard

* Use enhanced `switch`
* Use Truth.assertThat instead of JUnit Assert
* Use java.time.Duration as much as possible
* Mark some methods as deprecated
* Make it possible to toggle Bluetooth in EnableBluetoothRule

MUST_SLEEP=Legacy CTS code still use Thread.sleep(). Hence this library
cannot avoid it.

Bug: 300052980
Test: atest CtsBluetoothTestCases
Test: atest CtsRootBluetoothTestCases
Change-Id: If213d4512a432b601977fb1a6e4ff911d2450e8d