There is no standard encryption format for "file wallets". They are stored in plain text (raw ed25519 keypair encoded as a JSON integer array). This is mainly because their primary use is via the CLI tools which have no notion of a "session" so they would have to be unlocked for every invocation that needs to sign.
The types you specify aren't strictly required to work in the default manner with respect to storage though. Anyone developing a an application where encryption would be appropriate can implement it as they see fit. Web wallets for instance, do encrypt key material (bip39 mnemonic rather than raw keypair) before storing it in site session data. Sollet does it here. JS, not Rust, but trivial to implement in most languages