test: add missing testIDs for maestro selectors

Add testIDs to the fiat and crypto dropdown buttons in the ramp create scene
so UI tests can drive the fiat/crypto selectors by id.

Author: j0ntz

src/components/scenes/RampCreateScene.tsx

@@ -811,7 +811,10 @@ export const RampCreateScene: React.FC<Props> = (props: Props) => {
         {/* Amount Inputs */}
         {/* Top Input (Fiat) */}
         <View style={styles.inputRowView}>
-          <DropdownInputButton onPress={handleFiatDropdown}>
+          <DropdownInputButton
+            onPress={handleFiatDropdown}
+            testID="rampFiatDropdown"
+          >
             {selectedFiatFlagUri !== '' ? (
               <ShadowedView style={styles.shadowedIcon}>
                 <FastImage
@@ -861,7 +864,10 @@ export const RampCreateScene: React.FC<Props> = (props: Props) => {
             />
           ) : (
             <>
-              <DropdownInputButton onPress={handleCryptDropdown}>
+              <DropdownInputButton
+                onPress={handleCryptDropdown}
+                testID="rampCryptoDropdown"
+              >
                 {isLoadingPersistedCryptoSelection ? (
                   <ActivityIndicator />
                 ) : selectedCrypto == null || selectedWallet == null ? null : (