Use anyhow more idiomatically (#31052)

https://github.com/zed-industries/zed/issues/30972 brought up another
case where our context is not enough to track the actual source of the
issue: we get a general top-level error without inner error.

The reason for this was `.ok_or_else(|| anyhow!("failed to read HEAD
SHA"))?; ` on the top level.

The PR finally reworks the way we use anyhow to reduce such issues (or
at least make it simpler to bubble them up later in a fix).
On top of that, uses a few more anyhow methods for better readability.

* `.ok_or_else(|| anyhow!("..."))`, `map_err` and other similar error
conversion/option reporting cases are replaced with `context` and
`with_context` calls
* in addition to that, various `anyhow!("failed to do ...")` are
stripped with `.context("Doing ...")` messages instead to remove the
parasitic `failed to` text
* `anyhow::ensure!` is used instead of `if ... { return Err(...); }`
calls
* `anyhow::bail!` is used instead of `return Err(anyhow!(...));`

Release Notes:

- N/A

crates/client/src/socks.rs

@@ -1,5 +1,5 @@
 //! socks proxy
-use anyhow::{Context, Result, anyhow};
+use anyhow::{Context as _, Result};
 use http_client::Url;
 use tokio_socks::tcp::{Socks4Stream, Socks5Stream};
 
@@ -31,7 +31,7 @@ pub(crate) async fn connect_socks_proxy_stream(
         // If parsing the proxy URL fails, we must avoid falling back to an insecure connection.
         // SOCKS proxies are often used in contexts where security and privacy are critical,
         // so any fallback could expose users to significant risks.
-        return Err(anyhow!("Parsing proxy url failed"));
+        anyhow::bail!("Parsing proxy url failed");
     };
 
     // Connect to proxy and wrap protocol later