Replace environment variable parser with zed --printenv outputting JSON (#32637)

Closes: https://github.com/zed-industries/zed/issues/32445
Follow-up to: https://github.com/zed-industries/zed/pull/31799

Release Notes:

- Improved handling of environment variables

---------

Co-authored-by: Conrad Irwin <conrad@zed.dev>

crates/remote_server/src/main.rs

@@ -12,6 +12,9 @@ struct Cli {
     /// by having Zed act like netcat communicating over a Unix socket.
     #[arg(long, hide = true)]
     askpass: Option<String>,
+    /// Used for loading the environment from the project.
+    #[arg(long, hide = true)]
+    printenv: bool,
 }
 
 #[derive(Subcommand)]
@@ -55,6 +58,11 @@ fn main() {
         return;
     }
 
+    if cli.printenv {
+        util::shell_env::print_env();
+        return;
+    }
+
     let result = match cli.command {
         Some(Commands::Run {
             log_file,