Add Update-DotnetVersion script

[vbjay]

Updates dotnet SDK and Runtime versions together

Allows for

.\Scripts\Update-DotnetVersion.ps1

OR

.\Scripts\Update-DotnetVersion.ps1 7.0

resolves #10192

Proposed changes

• Add script to allow updating dotnet version to latest of current version used or passing in a specified version
• Update appveyor build to allow user to set flag that causes the latest version to be used in build. Useful to test version bump before applying the change.

Test methodology

• Ran script and verified change

Test environment(s)

Merge strategy

I agree that the maintainer squash merge this PR (if the commit message is clear).

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✒️ I contribute this code under The Developer Certificate of Origin.

[mstv]

+1 works as promised
file output as UTF8 would be useful
results could be printed on the console, too (although they are visible in GE)

[vbjay]

@mstv Sure. Making sure flipping flag on build works and I can add output and utf8 fix.

[vbjay]

@mstv Last check to make sure update script doesn't run when flag is off and then this is good to go.

[vbjay]

@mstv Verified. This is good to go.

You can manually run script to update or if wanting to see if sdk/runtime change breaks something change

to make appveyor run script before install.

Sample output

[RussKie]

Nice! Few comments primarily of stylistic nature.

[mstv]

👍