fix(crate_universe): pass OUTPUT_BASE as --output_base startup flag to bazel info (#4183)

## Problem

The `OUTPUT_BASE` env var was added to let CI environments supply the
output_base without relying on `bazel info`. However, the override is
applied **after** parsing the `bazel info` output:

```rust
let output = process::Command::new(bazel).arg("info")...output()?;
if !output.status.success() {
    bail!(output.status)    // <-- bails here when output_base is not writable
}
// ... parse output ...
if let Ok(path) = env::var("OUTPUT_BASE") {  // <-- never reached
    bazel_info.insert(...);
}
```

When `bazel info` fails (e.g. the default `~/.cache/bazel/...` is not
writable in a sandboxed CI), the function bails before `OUTPUT_BASE` is
ever checked — making the env var useless for its intended purpose.

## Fix

Pass `OUTPUT_BASE` as a `--output_base` Bazel **startup flag** (before
the subcommand):

```
bazel --output_base=/path/to/base info release output_base
```

Startup flags take effect before Bazel accesses any path, so it never
touches the default (possibly non-writable) output_base. The `bazel
info` subprocess runs normally and the post-parsing override is no
longer needed.

## Changes

- `crate_universe/src/cli/vendor.rs`: restructure `BazelInfo::try_new`
to optionally inject `--output_base` as a startup flag; remove the
post-parsing `OUTPUT_BASE` override.
- Removed `test_parse_bazel_info_output_base_env_override` since
`parse_bazel_info` no longer handles the `OUTPUT_BASE` override — the
existing `test_bazel_info` already covers the parsing logic.