Improve loading of submodules

[DmitryScaletta]

1. Don't load submodules with not installed optional dependencies

Some packages may have optional dependencies.
If there was an error during loading a submodue, and it's a missing optional dependency error, just skip this submodule.

Closes #1937

2. Skip submodules if they have already been loaded as a part of main module

Example: some-module

package.json

{
  "exports": {
    ".": {
      // ...
      "default": "./index.js"
    },
    "./submodule": {
      // ...
      "default": "./submodule.js"
    }
  }
}

index.js

export * from './submodule';

submodule.js

export const submodule = () => {};

The main module exports all from the submodule.
And the submodule exports a function with the same name as a submodule name.
So when loading the submodule, lib already have a property submodule.

Closes #1938

• tests and linter show no problems (npm t)
• tests are added/updated for bug fixes and new features
• code is properly formatted (npm run fmt)
• description of changes is added in CHANGELOG.md
• update .d.ts typings

[tshemsedinov]

Duplicate expression: lib[subName]

[DmitryScaletta]

This check is actually necessary here because in every other case (except the one I described above) lib[subName] and sub[subName] would be equal to undefined.

[tshemsedinov]

• We do not use double quotas ", use linter before commit
• Parsing error in a such way is not reliable, it's better to get text between two double quotas with metautil.between(e.message, '"', '"') see: https://github.com/metarhia/metautil/tree/master#strings-utilities
• e is a bad naming, better err or even error

[DmitryScaletta]

I used linter before commit.
It didn't fix the quotes.
Looks like prettier wants to use double quotes if string contains a single quote character: '

[tshemsedinov]

20 is a magic number

[tshemsedinov]

Double optional chaining is not ok in out codebase

[tshemsedinov]

You can just remove else here