fix: raise Apple platform minimums in SPM manifests to match FlutterFramework

[radomir9720]

Description

battery_plus, connectivity_plus, network_info_plus, package_info_plus and share_plus declare a Swift Package Manager dependency on FlutterFramework (which requires iOS 13.0 / macOS 10.15), but their Package.swift files still declare lower platform minimums (iOS 12.0 / macOS 10.14).

SwiftPM refuses to resolve this, because a package cannot support a lower platform version than a package it depends on. Building an app that consumes one of these plugins via SPM fails with:

error: The package product 'FlutterFramework' requires minimum platform version 13.0
for the iOS platform, but this target supports 12.0 (in target 'share_plus' from project 'share_plus')

This PR raises the SPM platform minimums to iOS 13.0 / macOS 10.15 for the affected packages, and bumps the corresponding example apps' deployment targets so they keep building against the raised minimums.

This mirrors the fix already applied to device_info_plus in #3891. Podspecs are intentionally left unchanged, matching that precedent (SwiftPM enforces the cross-package platform constraint; CocoaPods does not).

Changes

Package.swift platform minimums (iOS 12.0→13.0, macOS 10.14→10.15):

• battery_plus
• connectivity_plus
• network_info_plus
• package_info_plus
• share_plus

Example app deployment targets bumped to match:

• connectivity_plus example iOS (IPHONEOS_DEPLOYMENT_TARGET 12.0→13.0)
• all five example macOS apps (MACOSX_DEPLOYMENT_TARGET 10.14→10.15)

Checklist

• The change is limited to SPM manifest platform minimums + matching example deployment targets.
• Follows the precedent set by feat(device_info_plus): Updated Swift Package Manager setup for Flutter 3.44 #3891 for device_info_plus.