Intercept generates an invalid `.env` file when multiline variables are present

[jfmyers9]

Describe the bug When intercepting a deployment with a multi-line environment variable, telepresence intercept generates an invalid .env file which results in a failure when paired with --docker-run.

To Reproduce Steps to reproduce the behavior:

1. When I run telepresence intercept <deployment> --docker-run -- ...
2. I see docker: poorly formatted environment: variable '"keys": [' contains whitespaces.

Expected behavior

I don't really know because of https://github.com/moby/moby/issues/12997, but it would be great if we could at least have an .env file that is parseable and then document the multiline limitation.

I was thinking about this approach in which we escape the environment variable as ENV="...": https://github.com/jfmyers9/telepresence/commit/8dfb4599ec9d192208ab5fd2fcb14ff79d5d6f90 but it doesn't work as expected as Docker treats anything after the = literally.

Other options include:

• Collapsing it to one line with literal \n that need to be evaluated with echo -e or equivalent inside the container.
• Skipping multiline environment variables and logging a warning.
• Passing multiline environment variables using -e instead of the .env file.

Versions (please complete the following information):

• Output of telepresence version

Client: v2.7.0 (api v3)
Root Daemon: v2.7.0 (api v3)
User Daemon: v2.7.0 (api v3)

• Operating system of workstation running telepresence commands MacOS
• Kubernetes environment and Version [e.g. Minikube, bare metal, Google Kubernetes Engine] 1.20, EKS

Additional context Just looking for ideas.