feature-7527

[+] add wallet convert in com_tx_wallet
[+] add description about wallet convert in dap_cli_server_cmd_add
[+] wallet convert create backup file with timestump
[*] wallet list always show wallets files, not wallets names
[*] wallet list show backup wallets
[*] change wallet_len in dap_chain_wallet_save (look ticket 8990)

requested review from @roman.khlopkov

assigned to @roman.khlopkov

mentioned in commit d043e872

merged