Rename storage access methods

StorageKey's read and try_read are confusing, notably because of errors related to uninitialized storage.

try_read should be the default behavior and there should be extensive documentation of what happens with the storage initialization.

try_read should be renamed to read and read to read_unchecked, but this is a breaking and abrasive change, so we should consider a way of migrating the interface that doesn't startle the users.