Setting to toggle using `uv` for venvs and support new `uv` specific environment tag from PET

[eleanorjboyd]

From PET repo:

Issue:

microsoft/python-environment-tools#261

New Tag:

VenvUv, // Virtual environments created with UV
normally its Venv

comes from the nativeLocator

pub struct PyVenvCfg {
    pub version: String,
    pub version_major: u64,
    pub version_minor: u64,
    pub prompt: Option<String>,
    pub uv_version: Option<String>, // UV version if this was created by UV
}

parsing function

fn parse_uv_version(line: &str) -> Option<String> {
    let trimmed = line.trim();
    if trimmed.starts_with("uv") {
        if let Some(eq_idx) = trimmed.find('=') {
            let value = trimmed[eq_idx + 1..].trim();
            if !value.is_empty() {
                return Some(value.to_string());
            }
        }
    }
    None
}

Python Environments Extension Side

Setting:

introduce new setting python-envs.alwaysUseUv : boolean
default value: true

• This setting configures if uv will be used to manage all virtual environments if set to true, or only manage those explicitly created by uv when set to false.

Adjust venv manager and pip (ie whenever uv is checked) to also check this setting. If its of type uv, always do it with uv, otherwise check the setting

[eleanorjboyd]

this is done on the extension side, will still need to be completed on the PET side