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/workspace/src/pane_group.rs

@@ -3,7 +3,7 @@ use crate::{
     pane_group::element::pane_axis,
     workspace_settings::{PaneSplitDirectionHorizontal, PaneSplitDirectionVertical},
 };
-use anyhow::{Result, anyhow};
+use anyhow::Result;
 use call::{ActiveCall, ParticipantLocation};
 use collections::HashMap;
 use gpui::{
@@ -58,7 +58,7 @@ impl PaneGroup {
                     self.root = Member::new_axis(old_pane.clone(), new_pane.clone(), direction);
                     Ok(())
                 } else {
-                    Err(anyhow!("Pane not found"))
+                    anyhow::bail!("Pane not found");
                 }
             }
             Member::Axis(axis) => axis.split(old_pane, new_pane, direction),
@@ -538,7 +538,7 @@ impl PaneAxis {
                 }
             }
         }
-        Err(anyhow!("Pane not found"))
+        anyhow::bail!("Pane not found");
     }
 
     fn remove(&mut self, pane_to_remove: &Entity<Pane>) -> Result<Option<Member>> {
@@ -579,7 +579,7 @@ impl PaneAxis {
                 Ok(None)
             }
         } else {
-            Err(anyhow!("Pane not found"))
+            anyhow::bail!("Pane not found");
         }
     }