Export [test] utilities in umbrella package

[arboleya]

We should export all secondary entry points (utilities) using dedicated entry points in the fuels umbrella package.

For example:

• fuels/test-utils — all test utilities from all sub-packages
• fuels/cli-utils — all CLI utilities from all sub-packages

The idea is that each of these would consolidate all utilities of the same group.

A few examples I grabbed from the codebase:

import { generateTestWallet } from '@fuel-ts/account/test-utils';
import { expectToThrowFuelError } from '@fuel-ts/errors/test-utils';
import { findBinPath } from '@fuel-ts/utils/cli-utils';

The umbrella package should be the only thing users should have to deal with.

[nedsalk]

Related comment. That PR has implementation for how the infrastructure part of this issue would be handled.