Support Orleans 7.0

[cecilphillip]

Changes

• Upgraded dependent NuGet packages
• Bumped version to 0.0.44-pre
• Removed ApplicationPartManagerExtensions
• Switch from IGrainActivationContext to IGrainContext
• Updated samples

[cecilphillip]

@creyke seems like SagaGrain.cs has different line endings than the rest of the code. It's formatted with crlf while the others are lf.

I closed the previous PR and created this one with the mixed endings preserved since the previous was added tons of extra white space.

[creyke]

Thanks for this contribution. There was an expired NuGet key so I had to bump the version again for simplicity. The package is now available at: https://www.nuget.org/packages/Orleans.Sagas/0.0.45-pre

...and apologies for the line ending issue my side - thanks for working round it.