Make ED of zero (kind of) work (#13655)

* Minimum of 1 for ED

* Avoid need for ED to be minimum one

* Docs

* Ban ED of zero unless feature enabled

* use integrity_test

* Docs

* Cleanup

* Update frame/balances/Cargo.toml

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

* Update frame/balances/src/lib.rs

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

* Update frame/balances/src/lib.rs

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

* Ensure dodgy code is disabled by default

* zero_ed -> insecure_zero_ed

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Co-authored-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: parity-processbot <>