Add remove_from_table manifest util

Needed for `cargo remove`.

src/cargo/util/toml_mut/manifest.rs

@@ -368,6 +368,26 @@ impl LocalManifest {
         Ok(())
     }
 
+    /// Remove entry from a Cargo.toml.
+    pub fn remove_from_table(&mut self, table_path: &[String], name: &str) -> CargoResult<()> {
+        let parent_table = self.get_table_mut(table_path)?;
+
+        let dep = parent_table
+            .get_mut(name)
+            .filter(|t| !t.is_none())
+            .ok_or_else(|| non_existent_dependency_err(name, table_path.join(".")))?;
+
+        // remove the dependency
+        *dep = toml_edit::Item::None;
+
+        // remove table if empty
+        if parent_table.as_table_like().unwrap().is_empty() {
+            *parent_table = toml_edit::Item::None;
+        }
+
+        Ok(())
+    }
+
     /// Remove references to `dep_key` if its no longer present.
     pub fn gc_dep(&mut self, dep_key: &str) {
         let explicit_dep_activation = self.is_explicit_dep_activation(dep_key);
@@ -517,3 +537,10 @@ fn parse_manifest_err() -> anyhow::Error {
 fn non_existent_table_err(table: impl std::fmt::Display) -> anyhow::Error {
     anyhow::format_err!("the table `{table}` could not be found.")
 }
+
+fn non_existent_dependency_err(
+    name: impl std::fmt::Display,
+    table: impl std::fmt::Display,
+) -> anyhow::Error {
+    anyhow::format_err!("the dependency `{name}` could not be found in `{table}`.")
+}