Remove custom dotnet-install.ps1

[rhysparry]

Background

When downloading the .NET SDK during the build it would fail if the system did not enable TLS 1.2 by default. This is generally the case for older Windows versions.

This PR aims to move the modification into the build bootstrapper. This will mean that upstream fixes to the dotnet installer will be available immediately.

Why not TLS 1.3?

Prior to .NET Framework 4.8, TLS 1.3 was not available. Supporting TLS 1.3 would require special-casing these older versions.

Results

• Removes the custom dotnet-install.ps1 file
• Restores dotnet-install.ps1 usage in build.ps1
• Adds customization to build.ps1 to ensure TLS1.2 is enabled when the download script attempts to download the .NET SDK.

How to review this PR

Quality ✔️

Pre-requisites

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• I have considered appropriate testing for my change.