Support human numbers in config

Summary

With new updates you can execute picodata run --memtx-memory 1G and set up human numbers for parameter memtx-memory, same applicable in the config file.

Supported suffixes: K (Kilobytes), M (Megabytes), G (Gigabytes), T (Terabytes), 1K = 1024

By default still 64M is set up

e.g:

picodata run --memtx-memory 1000K

picodata run --memtx-memory 256M

picodata run --memtx-memory 10G

picodata run --memtx-memory 1T

or in the config file:

cluster:
    cluster_id: test
    tier:
        default:
instance:
    memtx:
        memory: 256K

• Close #637 (closed)
• Cherry-pick to: none
• Docs follow-up: docs#353 (closed)