feat: add codegen ios.componentProvider (#2572)

# Summary

Add a newly introduced field `ios.componentProvider` to the `codegen`
configuration to create an association map between JS components and
their native implementations.

When this field is defined, it is used and codegen don't crawl the file
system looking for the mapping. You can find the documentation for it
here:
https://github.com/facebook/react-native-website/pull/4388/files#diff-7fbb6ff2e58f8bd50d2763e551c63e1816adb6d593f40d489785b575b0e82718R76

## Test Plan

Running `pod install` in the `tests-example` will currently hang and
eventually crash, as it attempts to crawl through the entire repository.

package.json

@@ -135,6 +135,39 @@
     "jsSrcsDir": "./src/fabric",
     "android": {
       "javaPackageName": "com.horcrux.svg"
+    },
+    "ios": {
+      "componentProvider": {
+        "RNSVGCircle": "RNSVGCircle",
+        "RNSVGClipPath": "RNSVGClipPath",
+        "RNSVGDefs": "RNSVGDefs",
+        "RNSVGEllipse": "RNSVGEllipse",
+        "RNSVGFeBlend": "RNSVGFeBlend",
+        "RNSVGFeColorMatrix": "RNSVGFeColorMatrix",
+        "RNSVGFeComposite": "RNSVGFeComposite",
+        "RNSVGFeFlood": "RNSVGFeFlood",
+        "RNSVGFeGaussianBlur": "RNSVGFeGaussianBlur",
+        "RNSVGFeMerge": "RNSVGFeMerge",
+        "RNSVGFeOffset": "RNSVGFeOffset",
+        "RNSVGFilter": "RNSVGFilter",
+        "RNSVGForeignObject": "RNSVGForeignObject",
+        "RNSVGGroup": "RNSVGGroup",
+        "RNSVGImage": "RNSVGImage",
+        "RNSVGLine": "RNSVGLine",
+        "RNSVGLinearGradient": "RNSVGLinearGradient",
+        "RNSVGMarker": "RNSVGMarker",
+        "RNSVGMask": "RNSVGMask",
+        "RNSVGPath": "RNSVGPath",
+        "RNSVGPattern": "RNSVGPattern",
+        "RNSVGRadialGradient": "RNSVGRadialGradient",
+        "RNSVGRect": "RNSVGRect",
+        "RNSVGSvgView": "RNSVGSvgView",
+        "RNSVGSymbol": "RNSVGSymbol",
+        "RNSVGTSpan": "RNSVGTSpan",
+        "RNSVGText": "RNSVGText",
+        "RNSVGTextPath": "RNSVGTextPath",
+        "RNSVGUse": "RNSVGUse"
+      }
     }
   },
   "packageManager": "[email protected]"