Added java preloading sample to APIDemo. #1142

Job	Run time
Build (java/advanced/APIDemo)	3m 6s
Build (java/advanced/InlineAdaptiveBannerExample)	8s
Build (java/advanced/RewardedSSVExample)	9s
Build (kotlin/advanced/APIDemo)	4s
Build (kotlin/advanced/InlineAdaptiveBannerExample)	3s
Build (kotlin/advanced/JetpackComposeDemo)	5s
Build (java/admob/AppOpenExample)	7s
Build (java/admob/BannerExample)	7s
Build (java/admob/FullScreenNativeExample)	3s
Build (java/admob/InterstitialExample)	9s
Build (java/admob/NativeAdvancedExample)	6s
Build (java/admob/RewardedInterstitialExample)	4s
Build (java/admob/RewardedVideoExample)	7s
Build (kotlin/admob/AppOpenExample)	8s
Build (kotlin/admob/BannerExample)	9s
Build (kotlin/admob/InterstitialExample)	8s
Build (kotlin/admob/NativeAdvancedExample)	5s
Build (kotlin/admob/RewardedInterstitialExample)	7s
Build (kotlin/admob/RewardedVideoExample)	6s
Build (java/admanager/AppOpenExample)	8s
Build (java/admanager/BannerExample)	8s
Build (java/admanager/InterstitialExample)	10s
Build (java/admanager/NativeAdsExample)	7s
Build (java/admanager/RewardedInterstitialExample)	5s
Build (java/admanager/RewardedVideoExample)	7s
Build (kotlin/admanager/AppOpenExample)	4s
Build (kotlin/admanager/BannerExample)	4s
Build (kotlin/admanager/InterstitialExample)	13s
Build (kotlin/admanager/NativeAdsExample)	8s
Build (kotlin/admanager/RewardedInterstitialExample)	7s
Build (kotlin/admanager/RewardedVideoExample)	5s
	6m 27s

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