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/recent_projects/src/ssh_connections.rs

@@ -1,7 +1,7 @@
 use std::collections::BTreeSet;
 use std::{path::PathBuf, sync::Arc, time::Duration};
 
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use auto_update::AutoUpdater;
 use editor::Editor;
 use extension_host::ExtensionStore;
@@ -484,15 +484,14 @@ impl remote::SshClientDelegate for SshClientDelegate {
                 cx,
             )
             .await
-            .map_err(|e| {
-                anyhow!(
-                    "Failed to download remote server binary (version: {}, os: {}, arch: {}): {}",
+            .with_context(|| {
+                format!(
+                    "Downloading remote server binary (version: {}, os: {}, arch: {})",
                     version
                         .map(|v| format!("{}", v))
                         .unwrap_or("unknown".to_string()),
                     platform.os,
                     platform.arch,
-                    e
                 )
             })?;
             Ok(binary_path)