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/sqlez/src/connection.rs

@@ -6,7 +6,7 @@ use std::{
     ptr,
 };
 
-use anyhow::{Result, anyhow};
+use anyhow::Result;
 use libsqlite3_sys::*;
 
 pub struct Connection {
@@ -199,11 +199,7 @@ impl Connection {
                 )
             };
 
-            Err(anyhow!(
-                "Sqlite call failed with code {} and message: {:?}",
-                code as isize,
-                message
-            ))
+            anyhow::bail!("Sqlite call failed with code {code} and message: {message:?}")
         }
     }