fix(command-dev): align functions default env variables with production

Describe the bug

Related to https://github.com/netlify/cli/pull/2348

It seems Netlify Dev passes URL and DEPLOY_URL to functions, but in production we only pass URL.
We'll need to figure out what built-in ones are passed to functions and add those to the CLI.

To Reproduce

1. Clone the https://github.com/erezrokah/netlify-build-reproductions repo
2. Switch to the pr_2348 branch
3. ntl init
4. ntl deploy
5. Invoke the live function https://cli-pr-2348--<site>.netlify.app/.netlify/functions/index
6. ntl dev
7. Invoke the local function http://localhost:8888/.netlify/functions/index

See that the live function only returns the URL env variable and the local one returns DEPLOY_URL.

  System:
    OS: macOS 11.3
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 1.00 GB / 32.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 15.14.0 - ~/.nvm/versions/node/v15.14.0/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 7.11.1 - ~/.nvm/versions/node/v15.14.0/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  npmGlobalPackages:
    netlify-cli: 3.29.2

Expected behavior

Prod an dev environment should match

Additional context

https://docs.netlify.com/configure-builds/environment-variables/

Start with the reproduction steps comparing the deployed function invoked through the Netlify URL with the local function invoked by ntl dev, then review the environment-variable documentation linked in the issue. Done means the built-in environment variables exposed to functions in development match those exposed in production, including the expected handling of URL and DEPLOY_URL.