Rename visual_test_runner to zed_visual_test_runner (#46171)

This fixes the auto-update failure by ensuring cargo-bundle picks 'zed'
as the first binary.

**Problem:** `cargo metadata` returns binaries alphabetically, so
`visual_test_runner` was coming before `zed`. When cargo-bundle looks
for the first binary to bundle (without `--bin`), it was picking
`visual_test_runner` - which doesn't exist in release builds because it
requires the `visual-tests` feature.

The previous fix (#46163) added `--bin zed` to explicitly select the
binary, but this caused cargo-bundle to use the binary name ('zed')
instead of the bundle metadata name ('Zed Nightly'), breaking
auto-updates.

**Fix:** Rename the binary to `zed_visual_test_runner` so it comes after
`zed` alphabetically. This restores the original bundle script behavior
that has worked for years.

Also reverts the `--bin zed` workaround from #46163.

Release Notes:

- N/A

script/bundle-mac

@@ -100,7 +100,7 @@ sed \
     "s/package.metadata.bundle-${channel}/package.metadata.bundle/" \
     Cargo.toml
 
-app_path=$(cargo bundle ${build_flag} --target $target_triple --select-workspace-root --bin zed | xargs)
+app_path=$(cargo bundle ${build_flag} --target $target_triple --select-workspace-root | xargs)
 
 mv Cargo.toml.backup Cargo.toml
 popd