refactor(frontend): use #[derive(Fields)] in statement handlers

[wangrunji0408]

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What's changed and what's your intention?

Similar to #14947, this PR uses #[derive(Fields)] to help construct rows and schemas in statement handlers.

- Row::new(vec![
-     Some(info.name.clone().into()),
-     Some(info.setting.clone().into()),
-     Some(info.description.clone().into()),
- ])
+ ShowVariableAllRow {
+     name: info.name.clone(),
+     setting: info.setting.clone(),
+     description: info.description.clone(),
+ }

It also introduces an attribute to customize field name style:

#[derive(Fields)]
#[fields(style = "TITLE CASE")] // <--
struct ExplainRow {
    query_plan: String, // field name will be "QUERY PLAN"
}

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
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• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
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Documentation

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[BugenZhao]

LGTM!

[yezizp2012]

LGTM!