Update mcr.microsoft.com/dotnet/sdk Docker tag to v7

This MR contains the following updates:

Package	Type	Update	Change
mcr.microsoft.com/dotnet/sdk	image	major	6.0 -> 7.0
mcr.microsoft.com/dotnet/sdk	final	major	6.0 -> 7.0
mcr.microsoft.com/dotnet/sdk	stage	major	6.0 -> 7.0

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ConsoleAppExample/Dockerfile

 FROM mcr.microsoft.com/dotnet/runtime:6.0 AS base
 WORKDIR /app
 
-FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
+FROM mcr.microsoft.com/dotnet/sdk:7.0 AS build
 WORKDIR /src
 COPY ["DemoRunner/DemoRunner.csproj", "DemoRunner/"]
 RUN dotnet restore "DemoRunner/DemoRunner.csproj"