* mutate_exists for StorageValue with ValueQuery

Signed-off-by: muraca <[email protected]>

* added `#[crate::storage_alias]` to tests

Signed-off-by: muraca <[email protected]>

* added StorageEntryMetadata

Signed-off-by: muraca <[email protected]>

* Update frame/support/src/lib.rs

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Signed-off-by: muraca <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>