Hearing Aid Compatibility toggle functionality in Settings

FCC has clarified that all smart phone must have a feature to enable Hearing Aid Compatibility (HAC) mode in system setting menu.

Currently the HAC settings is located in Dialer app's accessibility settings
page. We move this settings to Settings > Accessibility > Hearing Aids
page to compliance the rule.

Bug: 233976673
Test: make RunSettingsRoboTests ROBOTEST_FILTER=HearingAidCompatibilityPreferenceControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AccessibilityHearingAidsFragmentTest
Change-Id: Iba773456fd96b40ab3487a335c163079d083d505