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/zed/src/main.rs

@@ -4,7 +4,7 @@
 mod reliability;
 mod zed;
 
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use clap::{Parser, command};
 use cli::FORCE_CLI_MODE_ENV_VAR_NAME;
 use client::{Client, ProxySettings, UserStore, parse_zed_link};
@@ -1073,7 +1073,7 @@ fn parse_url_arg(arg: &str, cx: &App) -> Result<String> {
             {
                 Ok(arg.into())
             } else {
-                Err(anyhow!("error parsing path argument: {}", error))
+                anyhow::bail!("error parsing path argument: {error}")
             }
         }
     }