Add remove_proxies API for pallet-proxies #7557 (#12714)

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Add remove_proxies API for pallet-proxies
#7557

* added remove_all_proxy_delegates method

* remove all proxy implementation

* remove_all_proxy_delegate

* reverted changes

* fixed 7557

* fixed warnings

* removed println! causing build failure on ci/cd pipelines

* incorporated suggested changes

* minor change

* made suggested changes

* method comment

* Update frame/proxy/src/lib.rs

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Co-authored-by: Juan <[email protected]>
Co-authored-by: parity-processbot <>