[templates] fix broken/wrong item template contents

[jonathanpeppers]

After working on #7349, I found some really odd behavior if you name an Android layout, my_cool_layout.xml.

VS appears to generate:

<?xml version="1.0" encoding="utf-8"?>
<Linearmy_cool_layout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:my_cool_layout_width="match_parent"
    android:my_cool_layout_height="match_parent">

</Linearmy_cool_layout>

This is completely broken! It appears that anywhere the word Layout was replaced with my_cool_layout. I also get the same behavior with dotnet new android-layout -n my_cool_layout.

To solve this issue, I made the default name Layout1, so that <LinearLayout/> and android:layout_width, are not replaced.

Now I get a my_cool_layout.xml with the contents:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</LinearLayout>

Secondly, the android-activity template if you run:

dotnet new android-activity -n MyActivity

It will generate:

[Activity(Label = "@string/app_name", MainLauncher = true)]
public class MyActivity : Activity

Let's replace the label with the name passed in, and remove MainLauncher=true, so we instead get:

[Activity(Label = "MyActivity")]
public class MyActivity : Activity

I think this will prevent confusion with multiple app launchers, etc.