fix(network-activity-plugin): avoid Metro optional dependency overlay for Nitro (callstackincubator#273)

## Summary
Move `react-native-nitro-fetch` resolution to module initialization so
the network activity plugin reads the optional dependency once before
React Native finishes initializing.

## Context
It's supposed to provide a workaround for Metro 0.82 bug, where optional
dependencies required at run-time, after react-native is initialized,
will show the error overlay. The changes done are moving the require
time to before react-native is fully initialized, just like we do
currently for `react-native-sse`, so the error overlay is never
displayed.

This keeps the existing fallback behavior for apps that do not install
`react-native-nitro-fetch`, but avoids re-running the optional require
from the nitro inspector enable path.

## Proposed Testing Scenario
1. Run an app that includes `@rozenite/network-activity-plugin` without
installing `react-native-nitro-fetch`.
2. Start and stop network recording multiple times after the app has
already initialized.
3. Confirm the app does not show the Metro error overlay for the missing
optional nitro dependency.
4. Run an app that does install `react-native-nitro-fetch` and verify
network recording still works for nitro-backed requests.

Author: V3RON

.changeset/five-owls-relax.md

@@ -0,0 +1,5 @@
+---
+'@rozenite/network-activity-plugin': patch
+---
+
+Resolve the optional `react-native-nitro-fetch` dependency before React Native finishes initializing so Metro 0.82 does not show an error overlay when the package is not installed.

packages/network-activity-plugin/src/react-native/nitro-fetch/get-nitro-module.ts

@@ -1,9 +1,13 @@
 import type { NitroModule } from './nitro-network-inspector';
 
-export const getNitroModule = (): NitroModule | null => {
+const nitroModule = (() => {
   try {
     return require('react-native-nitro-fetch') as NitroModule;
   } catch {
     return null;
   }
+})();
+
+export const getNitroModule = (): NitroModule | null => {
+  return nitroModule;
 };