Add search terms in random and expression categories (#7736)

# Description

Refers to: [5093](https://github.com/nushell/nushell/issues/5093)

# Tests

- [x] `cargo fmt --all -- --check` to check standard code formatting
(`cargo fmt --all` applies these changes)
- [x] `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- [x]  `cargo test --workspace` to check that all tests pass

crates/nu-command/src/random/bool.rs

@@ -31,6 +31,10 @@ impl Command for SubCommand {
         "Generate a random boolean value"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["generate", "boolean", "true", "false", "1", "0"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,

crates/nu-command/src/random/chars.rs

@@ -31,6 +31,10 @@ impl Command for SubCommand {
         "Generate random chars"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["generate", "character", "symbol", "alphanumeric"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,

crates/nu-command/src/random/decimal.rs

@@ -27,6 +27,10 @@ impl Command for SubCommand {
         "Generate a random decimal within a range [min..max]"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["generate", "float"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,

crates/nu-command/src/random/dice.rs

@@ -37,6 +37,10 @@ impl Command for SubCommand {
         "Generate a random dice roll"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["generate", "die", "1-6"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,

crates/nu-command/src/random/integer.rs

@@ -27,6 +27,10 @@ impl Command for SubCommand {
         "Generate a random integer [min..max]"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["generate", "natural", "number"]
+    }
+
     fn run(
         &self,
         engine_state: &EngineState,

crates/nu-command/src/random/uuid.rs

@@ -22,6 +22,10 @@ impl Command for SubCommand {
         "Generate a random uuid4 string"
     }
 
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["generate", "uuid4"]
+    }
+
     fn run(
         &self,
         _engine_state: &EngineState,