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/debugger_panel.rs

@@ -7,7 +7,7 @@ use crate::{
     ShowStackTrace, StepBack, StepInto, StepOut, StepOver, Stop, ToggleIgnoreBreakpoints,
     persistence,
 };
-use anyhow::{Result, anyhow};
+use anyhow::{Context as _, Result, anyhow};
 use command_palette_hooks::CommandPaletteFilter;
 use dap::StartDebuggingRequestArguments;
 use dap::adapters::DebugAdapterName;
@@ -1021,17 +1021,13 @@ impl DebugPanel {
                     }
 
                     workspace.update(cx, |workspace, cx| {
-                        if let Some(project_path) = workspace
+                        workspace
                             .project()
                             .read(cx)
                             .project_path_for_absolute_path(&path, cx)
-                        {
-                            Ok(project_path)
-                        } else {
-                            Err(anyhow!(
-                                "Couldn't get project path for .zed/debug.json in active worktree"
-                            ))
-                        }
+                            .context(
+                                "Couldn't get project path for .zed/debug.json in active worktree",
+                            )
                     })?
                 })
             })