Add CaptivePortalData fetching to NetworkMonitor

When a capport API URL is sent through notifyNetworkConnected or
notifyLinkPropertiesChanged, NetworkMonitor will (re)evaluate to
fetch the data, and report it back via notifyCaptivePortalDataChanged.

Test: atest NetworkStackTests NetworkStackNextTests
Bug: 139269711
Change-Id: I101e2b2799d399fa7b560bf5ea3d86dac7ba1be9

• apishim/29/com/android/networkstack/apishim/api29/CaptivePortalDataShimImpl.java[diff]
• apishim/30/com/android/networkstack/apishim/CaptivePortalDataShimImpl.java[diff]
• common/moduleutils/src/android/net/shared/IpConfigurationParcelableUtil.java[diff]
• common/networkstackclient/src/android/net/DhcpResultsParcelable.aidl[diff]
• src/com/android/server/connectivity/NetworkMonitor.java[diff]
• tests/unit/src/android/net/shared/IpConfigurationParcelableUtilTest.java[diff]
• tests/unit/src/com/android/server/connectivity/NetworkMonitorTest.java[diff]