Add search terms to into value (#13890)

# Description

From [Discord
today](https://discord.com/channels/601130461678272522/729071784321876040/1286904159047778316),
`into value` isn't classified with `conversions` like the other `into
...` subcommands. I think this is correct, since it's a `table->table`
operation, so it's a filter that has the side effect of (potentially)
converting (via inference) cell values.

But we should at least have some search terms that help here, so this PR
adds *"conversion"* and *"convert"* to the command.

# User-Facing Changes

`help -f conversion` will return `into value`

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

N/A

crates/nu-command/src/conversions/into/value.rs

@@ -32,7 +32,11 @@ impl Command for IntoValue {
     }
 
     fn description(&self) -> &str {
-        "Infer nushell datatype for each cell."
+        "Infer Nushell datatype for each cell."
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["convert", "conversion"]
     }
 
     fn examples(&self) -> Vec<Example> {