[Remote CryptoKeys] “remote” CryptoKeys should be renamed, suggest “syncable”

[othermaciej]

There’s no spec-meaningful way here in which the keys specified are “remote”. Specs can’t define where the key material is at rest or in memory. The distinct property of these keys that is observable and not an implementation detail is that they can sync between the user’s devices. A potential secondary benefit is that they can be written or read by certain native apps, but we may need a registry specifying how this is done for each distinct platform.