Remove source compatibility to java 8, in preparation for Gradle 8.5 upgrade

See #10740

android/AndroidManifest.xml

@@ -1,7 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
-    package="com.unciv.app" >
+    xmlns:tools="http://schemas.android.com/tools">
 
     <uses-sdk/>
 
@@ -10,6 +9,7 @@
     <!-- See https://developer.android.com/training/tv/start/start -->
     <uses-feature android:name="android.software.leanback" android:required="false" />
     <uses-feature android:name="android.hardware.touchscreen" android:required="false" />
+    <uses-feature android:glEsVersion="0x00020000" android:required="false" />
 
     <!--
         Known Lint warnings:

android/build.gradle.kts

@@ -27,6 +27,7 @@ android {
         resources.excludes += "DebugProbesKt.bin"
     }
     defaultConfig {
+        namespace = "com.unciv.app"
         applicationId = "com.unciv.app"
         minSdk = 21
         targetSdk = 33 // See #5044
@@ -65,9 +66,7 @@ android {
         disable += "MissingTranslation"   // see res/values/strings.xml
     }
     compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_1_8
         targetCompatibility = JavaVersion.VERSION_1_8
-
         isCoreLibraryDesugaringEnabled = true
     }
     androidResources {

core/build.gradle.kts

@@ -3,11 +3,6 @@ plugins {
     id("kotlin")
 }
 
-java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-}
-
-
 sourceSets {
     main {
         java.srcDir("src/")

desktop/build.gradle.kts

@@ -5,10 +5,6 @@ plugins {
     id("kotlin")
 }
 
-java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-}
-
 sourceSets {
     main {
         java.srcDir("src/")

ios/build.gradle.kts

@@ -7,10 +7,6 @@ sourceSets {
     }
 }
 
-java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-}
-
 tasks {
     compileJava {
         options.encoding = "UTF-8"

server/build.gradle.kts

@@ -4,10 +4,6 @@ plugins {
     id("kotlin")
 }
 
-java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-}
-
 sourceSets {
     main {
         java.srcDir("src/")

tests/build.gradle.kts

@@ -1,15 +1,6 @@
 import com.unciv.build.BuildConfig
 import org.gradle.api.tasks.testing.logging.TestLogEvent
 
-plugins {
-    id("java")
-}
-
-java {
-    sourceCompatibility = JavaVersion.VERSION_1_8
-    targetCompatibility = JavaVersion.VERSION_1_8
-}
-
 tasks {
     test {
         workingDir = file("../android/assets")