Add static methods for converting to and from wei with decimals

[Roman505050]

What feature should we add?

Add static methods for converting to and from wei with decimals to BaseWeb3

[michaelgirg]

Added the fix.

[Roman505050]

Added the fix.

Are you create a new pull request for this issue, yea? I solved this issue a long time ago in eth-utils and reuse functions for web3.py in #3769