Switch to using CDN for install script

[richlander]

We're relying on the install script being delivered via the website not the CDN. That needs to be changed, in both the .ps1 and .sh files

arcade/eng/common/tools.sh

Line 298 in f213557

local install_script_url="https://dotnet.microsoft.com/download/dotnet/scripts/$dotnetInstallScriptVersion/dotnet-install.sh"

There are also multiple references to the website.

arcade/eng/common/tools.sh

Lines 310 to 311 in f213557

	echo "Curl failed; dumping some information about dotnet.microsoft.com for later investigation"
	echo | openssl s_client -showcerts -servername dotnet.microsoft.com -connect dotnet.microsoft.com:443 || true

and

arcade/eng/common/tools.sh

Lines 56 to 58 in f213557

	# Enable repos to use a particular version of the on-line dotnet-install scripts.
	# default URL: https://dotnet.microsoft.com/download/dotnet/scripts/v1/dotnet-install.sh
	dotnetInstallScriptVersion=${dotnetInstallScriptVersion:-'v1'}

I see that the install script is actually in the same directory. Why not just use it?

https://github.com/dotnet/arcade/blob/main/eng/common/dotnet-install.sh