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/dap_adapters/src/javascript.rs

@@ -1,4 +1,5 @@
 use adapters::latest_github_release;
+use anyhow::Context as _;
 use dap::{StartDebuggingRequestArguments, adapters::DebugTaskDefinition};
 use gpui::AsyncApp;
 use std::{collections::HashMap, path::PathBuf, sync::OnceLock};
@@ -74,7 +75,7 @@ impl JsDebugAdapter {
                 .assets
                 .iter()
                 .find(|asset| asset.name == asset_name)
-                .ok_or_else(|| anyhow!("no asset found matching {:?}", asset_name))?
+                .with_context(|| format!("no asset found matching {asset_name:?}"))?
                 .browser_download_url
                 .clone(),
         })
@@ -98,7 +99,7 @@ impl JsDebugAdapter {
                 file_name.starts_with(&file_name_prefix)
             })
             .await
-            .ok_or_else(|| anyhow!("Couldn't find JavaScript dap directory"))?
+            .context("Couldn't find JavaScript dap directory")?
         };
 
         let tcp_connection = config.tcp_connection.clone().unwrap_or_default();