Finish RwLock

[rikosellic]

TODO

• Polish the Inv.
• RwLockUpgradeableGuard::drop.
• RwLockWriteGuard::drop.
• RwLockUpgradeableGuard::try_upgrade without ManuallyDrop.
• Define an exclusive ghost resource and replace the frac-based UniqueTokenStorage.
• Define a sum type resource that supports storage and borrowing.
• Use this resource in the Inv and prove RwLockReadGuard::Drop.

[rikosellic]

Well done. KVerus has done what I have expected. I will futhur impove try_upgrade after I finish verifying drop.