fix(proxy): make proxy task persistent (#10036)

### Description

`turbo watch dev` wasn't working properly with local proxies if they
were marked as `persistent` as they would be in a different run than the
proxy task.

This isn't a perfect fix as we're introducing the same failure to find
locally running dev tasks that *aren't* marked as persistent.

A few possible follow ups:
- Error on any dev tasks that aren't marked as persistent to ensure the
proxy ends up in the same run as the dev tasks.
- (Stretch): Lift requirement to have dev tasks marked as persistent,
this would probably require an overhaul of either `watch` or our `Run`
abstraction to "share" parts of one run with another.

### Testing Instructions

`turbo watch dev` with a microfrontend should no longer fail to find
which locally running apps dev tasks

crates/turborepo-lib/src/turbo_json/mod.rs

@@ -666,6 +666,7 @@ impl TurboJson {
                         "{mfe_package_name}#build"
                     )))])
                 }),
+                persistent: Some(Spanned::new(true)),
                 ..Default::default()
             }),
         );