boot(api): Add framework-nfc to NFC apex

Adding a conditional boot entry for framework-nfc.jar to be delivered
via NFC apex.

Also, rename the existing soong_config namespace for bootclasspath
entries to more generic "bootclasspath" (modified the existing usage to
match).

Bug: 303286040
Test: Compiles (with RELEASE_PACKAGE_NFC_STACK=NfcNci)
Test: Compiles (with RELEASE_PACKAGE_NFC_STACK=com.android.nfcservices)
Test: Device boots up after flashing
Test: atest CtsNfcTestCases
Change-Id: If170240fe60120a61dcceb68f9c581261aeee49f