cmd/clef, signer: initial poc of the standalone signer (#16154)
* signer: introduce external signer command
* cmd/signer, rpc: Implement new signer. Add info about remote user to Context
* signer: refactored request/response, made use of urfave.cli
* cmd/signer: Use common flags
* cmd/signer: methods to validate calldata against abi
* cmd/signer: work on abi parser
* signer: add mutex around UI
* cmd/signer: add json 4byte directory, remove passwords from api
* cmd/signer: minor changes
* cmd/signer: Use ErrRequestDenied, enable lightkdf
* cmd/signer: implement tests
* cmd/signer: made possible for UI to modify tx parameters
* cmd/signer: refactors, removed channels in ui comms, added UI-api via stdin/out
* cmd/signer: Made lowercase json-definitions, added UI-signer test functionality
* cmd/signer: update documentation
* cmd/signer: fix bugs, improve abi detection, abi argument display
* cmd/signer: minor change in json format
* cmd/signer: rework json communication
* cmd/signer: implement mixcase addresses in API, fix json id bug
* cmd/signer: rename fromaccount, update pythonpoc with new json encoding format
* cmd/signer: make use of new abi interface
* signer: documentation
* signer/main: remove redundant option
* signer: implement audit logging
* signer: create package 'signer', minor changes
* common: add 0x-prefix to mixcaseaddress in json marshalling + validation
* signer, rules, storage: implement rules + ephemeral storage for signer rules
* signer: implement OnApprovedTx, change signing response (API BREAKAGE)
* signer: refactoring + documentation
* signer/rules: implement dispatching to next handler
* signer: docs
* signer/rules: hide json-conversion from users, ensure context is cleaned
* signer: docs
* signer: implement validation rules, change signature of call_info
* signer: fix log flaw with string pointer
* signer: implement custom 4byte databsae that saves submitted signatures
* signer/storage: implement aes-gcm-backed credential storage
* accounts: implement json unmarshalling of url
* signer: fix listresponse, fix gas->uint64
* node: make http/ipc start methods public
* signer: add ipc capability+review concerns
* accounts: correct docstring
* signer: address review concerns
* rpc: go fmt -s
* signer: review concerns+ baptize Clef
* signer,node: move Start-functions to separate file
* signer: formatting
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