feat: add environment variable to disable progress output (#8600)

The changes in this commit introduce the `UV_NO_PROGRESS` environment
variable as an alternative way to control progress output suppression in
uv-cli, equivalent to using the `--no-progress` flag. This enhancement
simplifies configuration in CI environments and automated scripts by
eliminating the need to detect whether the script is running in a CI
environment.

Previously, disabling progress output required either passing the
`--no-progress` flag directly or implementing script logic to detect CI
environments and conditionally add the flag. With this change, users can
now simply set `UV_NO_PROGRESS=true` in their environment to achieve the
same effect.

The changes include:

- Adding the `UV_NO_PROGRESS` environment variable to the `EnvVars`
struct in `crates/uv-static/src/env_vars.rs`.
- Updating the `GlobalArgs` struct in `crates/uv-cli/src/lib.rs` to
include a new `no_progress` field that is bound to the `UV_NO_PROGRESS`
environment variable.
- Adding documentation for the new `UV_NO_PROGRESS` environment variable
in `docs/configuration/environment.md`.
## Test Plan

After creating a uv project using `uv init` in a temp directory in this
project:
```
cargo run cache clean && cargo run venv && UV_NO_PROGRESS=false cargo run sync 
cargo run cache clean && cargo run venv && cargo run sync  
```
produce the expected default behavior 

```
cargo run cache clean && cargo run venv && UV_NO_PROGRESS=false cargo run sync  
```
produces the same behavior as having the `--no-progress` flag.

crates/uv-cli/src/lib.rs

@@ -232,7 +232,7 @@ pub struct GlobalArgs {
     /// Hide all progress outputs.
     ///
     /// For example, spinners or progress bars.
-    #[arg(global = true, long)]
+    #[arg(global = true, long, env = EnvVars::UV_NO_PROGRESS, value_parser = clap::builder::BoolishValueParser::new())]
     pub no_progress: bool,
 
     /// Change to the given directory prior to running the command.