CLI key=value parser side quest (#30799)

There are a bunch of places where we needed to parse arguments of the type `key=value` into various different types.
The code had been duplicated a few times now, so this moves it into `common/` and uses some type magic to make it more versatile.

GitOrigin-RevId: eed6adc871910219068e31cdd02bd9c76df67a02

Author: gautamg795

Cargo.lock

@@ -8,6 +8,7 @@ license = "LicenseRef-FSL-1.1-Apache-2.0"
 doctest = false
 
 [dependencies]
+anyhow = { workspace = true }
 tracing = { workspace = true }
 tracing-appender = { workspace = true }
 tracing-subscriber = { workspace = true }

crates/cmd_util/Cargo.toml

@@ -0,0 +1,25 @@
+use std::str::FromStr;
+
+use anyhow::Context;
+
+pub fn parse_key_value<K, V, Output>(s: &str) -> anyhow::Result<Output>
+where
+    K: FromStr<Err: std::error::Error + Send + Sync + 'static>,
+    V: FromStr<Err: std::error::Error + Send + Sync + 'static>,
+    Output: TryFrom<(K, V)>,
+    anyhow::Error: From<<Output as TryFrom<(K, V)>>::Error>,
+{
+    let pos = s
+        .find('=')
+        .ok_or_else(|| anyhow::anyhow!("invalid key=value: no `=` found in `{s}`"))?;
+    let key = &s[..pos];
+    let value = &s[pos + 1..];
+    Ok((
+        key.parse()
+            .with_context(|| format!("Failed to parse key {key}"))?,
+        value
+            .parse()
+            .with_context(|| format!("Failed to parse value {value}"))?,
+    )
+        .try_into()?)
+}

crates/cmd_util/src/keyvalue.rs

@@ -1,2 +1,3 @@
 #![feature(lazy_cell)]
 pub mod env;
+pub mod keyvalue;