Move WASM singleton from `@iroha2/client` to `@iroha2/crypto-core`

[0x009922]

Description

Currently, @iroha2/client provides a mechanism to inject the crypto instance into the library, so that all crypto-related functions will work after that:

import { setCrypto } from '@iroha2/client'
import { crypto } from '@iroha2/crypto-target-node'

setCrypto(crypto)

The proposal is to move this singleton to the @iroha2/crypto-core package, because it seems to make more sense:

import { setCryptoWasm } from '@iroha2/crypto-core'
import { cryptoWasm } from '@iroha2/crypto-target-node'

setCryptoWasm(cryptoWasm)

After that, it will be probably possible to move all "interface wrap" into the single core package, and each crypto-target-* package will be a simple WASM exporter

Benefits

• More intuitive API: the crypto part is moved to the crypto package
• Simpler code base - no complicated wrap bundling for each target

Drawbacks

There might be some unexpected limitations, needs research.

[0x009922]

Closed by #199