[ObjC] add privacy manifests to grpc podspec (#35042)

Not sure if we need to do the same for all the podspec files.

Will create a separate PR for swift package.

Closes #35042

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35042 from HannahShiSFB:privacy-manifests c9b19d3c20
PiperOrigin-RevId: 588937122

gRPC.podspec

@@ -32,6 +32,8 @@ Pod::Spec.new do |s|
     :tag => "v#{version}",
   }
 
+  s.resource = 'src/objective-c/PrivacyInfo.xcprivacy'
+
   name = 'GRPCClient'
   s.module_name = name
   s.header_dir = name

src/objective-c/PrivacyInfo.xcprivacy

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>NSPrivacyTracking</key>
+	<false/>
+	<key>NSPrivacyCollectedDataTypes</key>
+	<array/>
+	<key>NSPrivacyTrackingDomains</key>
+	<array/>
+	<key>NSPrivacyAccessedAPITypes</key>
+	<array>
+		<dict>
+			<key>NSPrivacyAccessedAPIType</key>
+			<string>NSPrivacyAccessedAPICategoryFileTimestamp</string>
+			<key>NSPrivacyAccessedAPITypeReasons</key>
+			<array>
+				<string>C617.1</string>
+			</array>
+		</dict>
+	</array>
+</dict>
+</plist>

templates/gRPC.podspec.template

@@ -34,6 +34,8 @@
       :tag => "v#{version}",
     }
 
+    s.resource = 'src/objective-c/PrivacyInfo.xcprivacy'
+
     name = 'GRPCClient'
     s.module_name = name
     s.header_dir = name