Pull code from unmaintained prisma-yml package into prisma-loader package.

[andrewmcgivery]

This PR looks to address #1813 wherein a high severity vulnerability is present in prisma-yml that isn't being patched. To fix this, the code from prisma-yml has been pulled into the prisma-loader package.

Some notes about this merge:

• There is some less than ideal code in here coming in from the downstream repo. I made it pass the build and ESLINT on this repo but had to do a lot of not so ideal things such as usage of any, eslint ignores, and ts-ignores
• I brought the tests from the downstream repo. I cannot vouch for their quality.

All tests passing:

Linted:

Vulnerability is mitigated:

[ardatan]

Thank you @andrewmcgivery ! That's awesome!

[theguild-bot]

The latest changes of this PR are available as alpha in npm: 6.0.16-alpha-b57b03b9.0

Quickly update your package.json by running:

npx match-version @graphql-tools 6.0.16-alpha-b57b03b9.0