Add support for running python projects

[wmeints]

This PR introduces support for running Python projects as part of an Aspire solution. I took the NodeJS extension as inspiration but had to add a couple of extra pieces of logic since Python is a lot less standardized when it comes to how projects are structured.

Initially I created this project: https://github.com/wmeints/aspire-python but I feel that this PR is a much more useful way to add support for Python. I think it's a great resolution for #2760.

Assumptions made by the extension

• Your python project has a virtual environment located under .venv. Although you can change that.
• You have a Dockerfile for publishing the project to test/acceptance/production environments.

[mitchdenny]

@davidfowl I've been thinking about things like Node.js (and now Python). I'm wondering if whether to make things easier for people we should create a boilerplate Dockerfile if one doesn't already exist. The idea being that it gives people a starting point.

So if someone does AddPython...) and points at a particular directory we'll drop down a Dockerfile and .dockerignore file if one doesn't already exist. Then the can tweak it from there customizing the base image etc.

[davidfowl]

I don't think we should be writing files to disk using these APIs, but I like the idea that they would publish as a docker file by default. The publish operation would throw because it couldn't find one. That would instruct the user to add one for their language.

[wmeints]

I can see I broke the build because I forgot to update the playground apphost. I will do that tomorrow morning (GMT+1)

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mitchdenny]

@radical I think we need to kick the tests in Aspire.Hosting.Tests that were recently enabled for CI back to local only until we can fix the issue of the port conflicts.

[mitchdenny]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mitchdenny]

/azp run

[mitchdenny]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mitchdenny]

@wmeints thanks so much for your contribution to .NET Aspire. We'll be shipping your work in .NET Aspire 8.1!

[dotnet-bot]

‼️ Found issues ‼️

Project	Coverage Type	Expected	Actual
Aspire.StackExchange.Redis	Branch	42	41.35 🔻

Full code coverage report: https://dev.azure.com/dnceng-public/public/_build/results?buildId=720670&view=codecoverage-tab

[wmeints]

Excited to see this appear in 8.1! And thanks again for all the reviews and patience. I learned a lot from this experience. I'm coming back for more 😄

[mitchdenny]

@wmeints I'm writing up the blog post for .NET Aspire 8.1 are you happy for me to link to your GitHub profile for this contribution?

[wmeints]

@mitchdenny Feel free to link my profile in the blogpost :-)