Provide suffices for amount of cycles

[pakhomov-dfinity]

E.g. dfx canister --network=testnet deposit-cycles 10G bitcoin. Counting zeros is an unpleasant user experience.

[ericswanson-dfinity]

Implemented in #3452 and available in dfx 0.15.2

Certain suffixes that replace a number of zeros are now supported. The (case-insensitive) suffixes are:

• k for 000, e.g. 500k
• m for 000_000, e.g. 5m
• b for 000_000_000, e.g. 50B
• t for 000_000_000_000, e.g. 0.3T

For cycles an additional c or C is also acceptable. For example: dfx canister deposit-cycles 3TC mycanister