Support project-specific aspire doctor checks

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

`aspire doctor` currently checks general Aspire development prerequisites, but projects often have additional machine-level requirements that are specific to that solution.

For example, a project may require a particular ODBC driver, native SDK, CLI tool, certificate, or other locally installed dependency. Today these requirements are typically only discovered when the application fails to start, or they have to be checked through separate project-specific scripts.

This makes developer onboarding and troubleshooting less consistent than it could be.

### Describe the solution you'd like

Allow an Aspire project to contribute project-specific checks to aspire doctor.

Running:

`aspire doctor`

from within a project should include both the standard Aspire diagnostics and any diagnostics defined by that project, without requiring the application resources to be started.

This would provide a single, discoverable command for verifying that a development machine is ready to run a particular Aspire solution.

### Additional context

A concrete example is a Python resource using pyodbc that requires Microsoft ODBC Driver 18 for SQL Server to be installed on the developer machine.

Without a project-specific prerequisite check, the missing driver is only discovered later through an indirect runtime connection error.

Start with the `aspire doctor` entry point and its existing standard diagnostics. Determine how a project can contribute checks that run without starting application resources, using the Python `pyodbc` and Microsoft ODBC Driver 18 example as a concrete case. Done means project-specific prerequisites appear alongside the standard diagnostics when the command runs from that project.

Written by the indexing model from the issue text.