Second attempt to cosmwasm-core

[webmaster128]

Right now on main, the existence cosmwasm-core creates all sorts of indirections an undesired dependencies that we want to avoid. So let's revert the current approach.

A new attempt to pull out cosmwasm-core that we may or may not do should have the following properties

• does not depend on cosmwasm-crypto (not at runtime, not as dev-dependency)
• does not pull in the StdError type

One way to do that is to ensure the error types for the relevant symbols are not StdError.

• Avoid renaming symbols whenever possible (StdError/CoreError causes confusion)
• from_base64 can get it's own InvalidBase64Error
• HexBinary can get its own InvalidDataSizeError
• For the integer and decimal types create a dedicated error type for the impl TryFrom<&str>, all the other errors are already specialized
• ...

Those new errors can then be converted to StdError in cosmwasm-std.