[Bug] Pnpify SDK generation errors out if eslint is not installed

**Describe the bug**



Pnpify SDK generation errors out if eslint is not installed



**To Reproduce**



```

$ yarn add @yarnpkg/pnpfiy

$ yarn pnpify --sdk

Error: A package is trying to access a peer dependency that should be provided by its direct ancestor but isn't



Required package: eslint (via "eslint/package.json")

Required by: @yarnpkg/pnpify@virtual:402e3d2070e057bc1180d1d078c776cf4354afb6d37c93585b0815585e67d99d546134f307b9b6f4fd5571ee37e4b3a0a2615e9ac1469dd97759c388c70244bb#npm:2.0.0-rc.3 (via /Users/victor/work/larix/.yarn/virtual/@yarnpkg-pnpify-virtual-9e4a182610/0/cache/@yarnpkg-pnpify-npm-2.0.0-rc.3-48ed462780.zip/node_modules/@yarnpkg/pnpify/lib/dynamicRequire.js)



    at Object.makeError (/Users/victor/work/larix/.pnp.js:9151:26)

    at resolveToUnqualified (/Users/victor/work/larix/.pnp.js:11549:43)

    at resolveRequest (/Users/victor/work/larix/.pnp.js:11604:31)

    at Object.resolveRequest.maybeLog [as resolveRequest] (/Users/victor/work/larix/.pnp.js:11643:32)

    at Function.module_1.default._resolveFilename (/Users/victor/work/larix/.pnp.js:11074:37)

    at Function.module_1.default._load (/Users/victor/work/larix/.pnp.js:10995:45)

    at Module.require (internal/modules/cjs/loader.js:637:17)

    at Object.require [as dynamicRequire] (internal/modules/cjs/helpers.js:22:18)

    at Object.exports.generateEslintWrapper (/Users/victor/work/larix/.yarn/virtual/@yarnpkg-pnpify-virtual-9e4a182610/0/cache/@yarnpkg-pnpify-npm-2.0.0-rc.3-48ed462780.zip/node_modules/@yarnpkg/pnpify/lib/generateSdk.js:49:112)



```



**Proposed approach to fix the issue**

We can generate SDK only for the packages that are installed in the project and skip SDK generation for those that are not.



**Sherlock repro**

``` js repro

await packageJsonAndInstall({

  "devDependencies": {

    "@yarnpkg/pnpify": "^2.0.0-rc.3",

    "typescript": "^3.6.3"

  }

});

await expect(yarn(`pnpify`, `--sdk`)).rejects.not.toThrow('Command failed');

```

[
  {
    "category": "conflict",
    "rule": "signature.incompatible_declared_requirements",
    "source": "failure_signature",
    "excerpt": "Error: A package is trying to access a peer dependency that should be provided by its direct ancestor but isn't"
  }
]