Issue-11796: Provide more descriptive message for uv run pythonx.xx

[JWLee89]

Related Issue

#11796

Summary

1. Add meaningful message when user invokes uv with run python<valid-python-version>.
   ✅ "python", "python3", "python3.9", "python4", "python3.10", "python3.13.3", "python39" (yes, python39 might still be released in 100 years 😆 )

❌ "python3abc", "python3.12b3", "", "python-foo"

2. Contextual information added depending on whether the command was run inside of a uv project or not. See: https://github.com/astral-sh/uv/pull/12201/files#diff-423c3a82aab6dba4068dd7675391fc9328a66682131dbf2043e7847ab4ba8661R1092

Automated Tests

1. Added unit test for new functions created for parsing and validating python executable entered by user
2. TODO: Once specs are finalized through discussions in PR, will create integration tests if necessary

Need to Discuss

1. Invoking python via its patch version - E.g. python3.11.9 is invalid. However, uv supports uv run -p 3.11.9 python, which is why when we do the following:

uv run python3.11.9

We will get the following error:

error: Failed to spawn: `python3.11.9`
  Caused by: `python3.11.9` not available in the environment, which uses python `3.11.9`. Did you mean to search for a Python 3.11.9 environment with `uv run -p 3.11.9 python`?

Is this okay? If not, we need to define the specs in the PR here.

2. Supported python executable specs are defined as:

• is stable version
• is not post version

See:https://github.com/astral-sh/uv/pull/12201/files#diff-423c3a82aab6dba4068dd7675391fc9328a66682131dbf2043e7847ab4ba8661R1572-R1574

Would this be okay?
We can change the specs if needed. Lets discuss.

Manual Test

Case 1: run outside of project

1. Case where no project is created. Look for a python executable version that is not available in my local machine (in my case, it was python3.9)
2. Run cargo run -- run python3.9.3

error: Failed to spawn: `python3.9.3`
  Caused by: `python3.9.3` not available in the environment, which uses python `3.11.9`. Did you mean to search for a Python 3.9.3 environment with `uv run -p 3.9.3 python`?

4. Run cargo run -- run python3.9

error: Failed to spawn: `python3.9`
  Caused by: `python3.9` not available in the environment, which uses python `3.11.9`. Did you mean to search for a Python 3.9 environment with `uv run -p 3.9 python`?

5. Run cargo run -- run python3.11

Running `target/debug/uv run python3.11`
Python 3.11.9 (main, Apr  2 2024, 08:25:04) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

6. Run cargo run -- run python3.11.9

 Running `target/debug/uv run python3.11.9`
error: Failed to spawn: `python3.11.9`
  Caused by: `python3.11.9` not available in the environment, which uses python `3.11.9`. Did you mean to search for a Python 3.11.9 environment with `uv run -p 3.11.9 python`?

IMPORTANT: Is this acceptable? Invoking python by its patch version is not supported, so this is the expected behavior, but we need to discuss whether this behavior is acceptable.

Case 2: run inside of project

Create project using uv init example-app

1. uv run python3.13

error: Failed to spawn: `python3.13`
  Caused by: `python3.13` not available in the project environment, which uses python `3.12.5`. Did you mean to change the environment to Python 3.13 with `uv run -p 3.13 python`?

2. uv run python3

uv run python3
Python 3.12.5 (main, Aug  6 2024, 19:08:49) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.