feat(linter/no-unused-vars): delete non-root arrows, skip await

[DonIsaac]

This PR updates no-unused-var's fixer for VariableDeclarators in two ways:

1. Unused function expressions and arrow functions not declared in the top scope
   will now be removed.

   // not deleted, no change
   const x = function() {}
   const y = (a) => a
   function z() {}
   
   // new behavior
   function foo() {            // <- not deleted
       const x = () => {}      // <- deleted
       const y = function() {} // <- this too
   }

2. Variables initialized to an await expression will not be deleted.

   // unused await-initialized variables are often API calls with side effects
   // in the real world; we don't want to delete these.
   const res = await createUser(data)

[DonIsaac]

• feat(linter/no-unused-vars): delete non-root arrows, skip await #5083 👈
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging #5083 will not alter performance

_{Comparing don/08-22-feat_linter/no-unused-vars_delete_non-root_arrows_skip_await_ (a86d88f) with main (4a57086)}

Summary

✅ 29 untouched benchmarks