crypto: configure key sharing strategy based on DeviceIsolationMode (#4425)
* crypto: configure key sharing strategy based on deviceIsolationMode
fix eslint import error
cryptoMode was renamed to deviceIsolationMode
post rebase fix: Device Isolation mode name changes
* Fix outdated docs referring to old cryptomode
* code review: better comment for globalBlacklistUnverifiedDevices option
* RoomEncryptor: Use appropriate default for getBlacklistUnverifiedDevices
* do not provide a default value for DeviceIsolationMode for encryption
* Update src/rust-crypto/RoomEncryptor.ts
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Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>