Back up peak refresh rate and min refresh rate

It's possible that in the future the peak refresh rate setting will have multiple values (e.g. 90, 120). For that reason, we shouldn't convert it to a boolean like in the previous CLs (ag/24604787, ag/24604847).

- set peak/min refresh rate to infinity if it's the highest refresh rate so that when we restore the setting on another device, we also choose the highest refresh rate
- back up peak/min refresh rate and add validators
- upgrade settings in SettingsProvider
- create a utils class - RefreshRateSettingsUtils

Bug: 211737588
Bug: 299552529
Test: atest DisplayModeDirectorTest
Test: atest ForcePeakRefreshRatePreferenceControllerTest
Test: atest PeakRefreshRatePreferenceControllerTest
Test: atest SettingsBackupTest
Test: atest SettingsProviderTest
Test: atest RefreshRateSettingsUtilsTest
Change-Id: I51f65bdc933273d9129c95e11494db37e659199a