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/debugger_ui/src/persistence.rs

@@ -1,3 +1,4 @@
+use anyhow::Context as _;
 use collections::HashMap;
 use dap::{Capabilities, adapters::DebugAdapterName};
 use db::kvp::KEY_VALUE_STORE;
@@ -96,18 +97,14 @@ pub(crate) async fn serialize_pane_layout(
     adapter_name: DebugAdapterName,
     pane_group: SerializedLayout,
 ) -> anyhow::Result<()> {
-    if let Ok(serialized_pane_group) = serde_json::to_string(&pane_group) {
-        KEY_VALUE_STORE
-            .write_kvp(
-                format!("{DEBUGGER_PANEL_PREFIX}-{adapter_name}"),
-                serialized_pane_group,
-            )
-            .await
-    } else {
-        Err(anyhow::anyhow!(
-            "Failed to serialize pane group with serde_json as a string"
-        ))
-    }
+    let serialized_pane_group = serde_json::to_string(&pane_group)
+        .context("Serializing pane group with serde_json as a string")?;
+    KEY_VALUE_STORE
+        .write_kvp(
+            format!("{DEBUGGER_PANEL_PREFIX}-{adapter_name}"),
+            serialized_pane_group,
+        )
+        .await
 }
 
 pub(crate) fn build_serialized_layout(