Simplify environment loading code (#40531)

This is a refactoring PR to simplify our environment loading code by:

- Getting rid of `EnvironmentErrorMessage` in favor of using
`anyhow::Result` everywhere, with a separate `mpsc` channel to
communicate statuses that will be shown in the activity indicator
- Inlining some functions that were only called once to reduce
indirection
- Removing the separate `direnv` module

Release Notes:

- N/A

crates/util/src/util.rs

@@ -353,7 +353,10 @@ pub async fn load_login_shell_environment() -> Result<()> {
     // into shell's `cd` command (and hooks) to manipulate env.
     // We do this so that we get the env a user would have when spawning a shell
     // in home directory.
-    for (name, value) in shell_env::capture(get_system_shell(), &[], paths::home_dir()).await? {
+    for (name, value) in shell_env::capture(get_system_shell(), &[], paths::home_dir())
+        .await
+        .with_context(|| format!("capturing environment with {:?}", get_system_shell()))?
+    {
         unsafe { env::set_var(&name, &value) };
     }
 
@@ -627,7 +630,7 @@ where
 }
 
 pub fn log_err<E: std::fmt::Debug>(error: &E) {
-    log_error_with_caller(*Location::caller(), error, log::Level::Warn);
+    log_error_with_caller(*Location::caller(), error, log::Level::Error);
 }
 
 pub trait TryFutureExt {