Availability checks for APermissionManager and AParcel functions

[marcprux]

When building with the nightly-6.3 SDK (see #27), we check for availability for various API. This highlights a couple of functions that require later version of Android, such as the Android (nightly-6.3, aarch64, 29) build:

/Users/runner/work/Android/Android/Sources/AndroidManifest/PermissionCheck.swift:78:13: error: 'APermissionManager_checkPermission' is only available in Android 31 or newer
 45 | }
 46 | 
 47 | public extension Permission {
    |        `- note: add '@available' attribute to enclosing extension
 48 |     
 49 |     /// Checks this permission for a specific process/user pair using
    :
 68 |     ///   - uid: User ID to evaluate. Defaults to the current user ID.
 69 |     /// - Returns: Permission check status.
 70 |     internal func _check(
    |                   `- note: add '@available' attribute to enclosing instance method
 71 |         pid: pid_t = getpid(),
 72 |         uid: uid_t = getuid()
    :
 76 |         #if os(Android)
 77 |         returnCode = rawValue.withCString {
 78 |             APermissionManager_checkPermission($0, pid, uid, &result)
    |             |- error: 'APermissionManager_checkPermission' is only available in Android 31 or newer
    |             `- note: add 'if #available' version check
 79 |         }
 80 |         #else

and the Android (nightly-6.3, aarch64, 31) build:

/Users/runner/work/Android/Android/Sources/AndroidBinder/Parcel.swift:675:9: error: 'AParcel_marshal' is only available in Android 33 or newer
 620 | // MARK: - Handle: Position & Size
 621 | 
 622 | internal extension Parcel.Handle {
     |          `- note: add '@available' attribute to enclosing extension
 623 | 
 624 |     /**
     :
 672 |      * Available since API level 33.
 673 |      */
 674 |     func marshal(into buffer: UnsafeMutablePointer<UInt8>, start: Int, length: Int) -> Result<Void, AndroidBinderError> {
     |          `- note: add '@available' attribute to enclosing instance method
 675 |         AParcel_marshal(pointer, buffer, start, length).mapError()
     |         |- error: 'AParcel_marshal' is only available in Android 33 or newer
     |         `- note: add 'if #available' version check
 676 |     }
 677 | 

You might consider guarding these within if #available(Android 33, *) { checks, which was added in swiftlang/swift#84574 and so will require the 6.3 SDK + NDK 28+.