Remove isHermesV1 from Babel preset (#56754)

Summary:
Pull Request resolved: #56754

Hermes V1 (Static Hermes) is now always enabled. Remove the isHermesV1 variable and inline its effects:
- enableRegenerator is always based on dev mode (was isHermesV1 && dev)
- preserveClasses is always true (was isHermesV1)

Also update the comments to drop the 'V1' framing.

## Changelog:
[Internal] -

Reviewed By: cortinico

Differential Revision: D104649639

Author: cipolleschi

packages/react-native-babel-preset/src/configs/main.js

@@ -57,25 +57,25 @@ const getPreset = (src, options, babel) => {
 
   const dev = options?.dev ?? babel?.env('development') ?? false;
 
-  // Hermes V1 (aka Static Hermes) uses more optimised profiles.
-  // There is currently no difference between stable and canary, but canary
-  // may in future be used to test features in pre-prod Hermes versions.
-  const isHermesV1 =
+  // Hermes V1 uses more optimised transform profiles. There is currently no
+  // difference between stable and canary, but canary may in future be used to
+  // test features in pre-prod Hermes V1 versions.
+  const isHermesProfile =
     transformProfile === 'hermes-stable' ||
     transformProfile === 'hermes-canary';
 
-  // We enable regenerator in dev builds for the time being because
+  // We enable regenerator in Hermes V1 dev builds for the time being because
   // Hermes V1 doesn't yet fully support debugging native generators.
   // (e.g. - it's not possible to inspect local variables when paused in a
   // generator).
   //
   // Use native generators in release mode because it has already yielded perf
-  // wins. The next release of Hermes will close this gap, so this won't
+  // wins. The next release of Hermes V1 will close this gap, so this won't
   // be permanent.
-  const enableRegenerator = isHermesV1 && dev;
+  const enableRegenerator = isHermesProfile && dev;
 
-  // Preserve class syntax and related if we're using Hermes V1.
-  const preserveClasses = isHermesV1;
+  // Preserve class syntax and related features for Hermes V1 profiles.
+  const preserveClasses = isHermesProfile;
 
   // Preserve private class fields and methods if the experiment is enabled.
   const preserveClassPrivate = TRUE_VALS.has(