upgrade cargo-ledger rust edition to 2021 #509

Job	Run time
Run static analysis (nanos, include_gif)	1m 23s
Build SDK (nanos)	2m 13s
Run static analysis (nanos, testmacro)	1m 16s
Build SDK (nanox)	2m 20s
Run static analysis (nanos, ledger_secure_sdk_sys)	1m 50s
Run static analysis (nanos, ledger_device_sdk)	2m 14s
Build SDK (nanosplus)	2m 16s
Run static analysis (nanox, include_gif)	1m 26s
Build SDK (stax)	2m 23s
Run static analysis for cargo-ledger	1m 30s
Run static analysis (nanox, testmacro)	1m 16s
Build SDK (flex)	2m 21s
Run static analysis (nanox, ledger_secure_sdk_sys)	1m 58s
Check code formatting	1m 8s
Run static analysis (nanox, ledger_device_sdk)	2m 15s
Run static analysis (nanosplus, include_gif)	1m 20s
Run static analysis (nanosplus, testmacro)	1m 18s
Build SDK	1m 36s
Run static analysis (nanosplus, ledger_secure_sdk_sys)	1m 50s
Run static analysis (nanosplus, ledger_device_sdk)	2m 22s
Run unit and integration tests (nanos)	2m 29s
Run static analysis (stax, include_gif)	1m 20s
Run unit and integration tests (nanox)	2m 38s
Run static analysis (stax, testmacro)	1m 15s
Run unit and integration tests (nanosplus)	2m 29s
Run static analysis (stax, ledger_secure_sdk_sys)	1m 59s
Run unit and integration tests (stax)	2m 52s
Run static analysis (stax, ledger_device_sdk)	2m 26s
Run unit and integration tests (flex)	2m 32s
Run static analysis (flex, include_gif)	1m 21s
Run static analysis (flex, testmacro)	1m 10s
Run static analysis (flex, ledger_secure_sdk_sys)	2m 1s
Run static analysis (flex, ledger_device_sdk)	2m 24s
	1h 3m 11s

Provide feedback