Define PRODUCT_HIDL_ENABLED

This is used to force HIDL to be enabled for device bring-up when
partners have converted all of their AOSP HAL implementations to AIDL,
but still have some partner-owned interfaces that they are working on
converting from HIDL TO AIDL.

Test: PRODUCT_HIDL_ENABLED = true && adb shell lshal
Test: PRODUCT_HIDL_ENABLED = false && adb shell lshal
Bug: 332548148

Change-Id: I6e6dc6c9e22d31c270e3c3520fc074bbeb349808