Change type of Env.root to AmbientAuth

[SeanTAllen]

Implements RFC #65.

Closes #3557.

This is going to break a lot of stuff.

No changes needed:

• appdirs (no PR needed)
• reactive_streams (no PR needed)
• regex (no PR needed)
• crypto (no PR needed)

First round changes:

• pony-patterns (2 patterns- one Supply Chain requires extensive work)
• ponycheck
• net_ssl
• peg
• semver
• tutorial (derived-authority, serialisation)
• corral
• fork_join

Second round changes:

• http (needs net_ssl versioned first, this can be a 2nd round change)
• glob (needs regex versioned first, this can be a 2nd round change)
• valbytes (needs ponycheck versioned first, this can be a 2nd round change)
• changelog-tool (requires peg to be versioned first)
• rfc-tool (requires peg to be versioned first)

Third round changes:

• http-server (needs net_ssl, valbytes, ponycheck versioned first. this is a 3rd round change)
• ponyup (requires http to be versioned first)
• templates (requires peg and valbytes to be versioned first)
• github_rest_api (requires http and peg to be versioned first)

[ponylang-main]

Hi @SeanTAllen,

The changelog - changed label was added to this pull request; all PRs with a changelog label need to have release notes included as part of the PR. If you haven't added release notes already, please do.

Release notes are added by creating a uniquely named file in the .release-notes directory. We suggest you call the file 3962.md to match the number of this pull request.

The basic format of the release notes (using markdown) should be:

## Title

End user description of changes, why it's important,
problems it solves etc.

If a breaking change, make sure to include 1 or more
examples what code would look like prior to this change
and how to update it to work after this change.

Thanks.