Fix Octopus.Client references for dotnet-script

[IsaacCalligeros95]

There were several issues with the rollout of the dotnet-script update, namely the comms and lack of customer awareness. During this a few issues were raised:

• References to Octopus.Client conflict with the Octopus class in the bootstrapper and throw errors when using it i.e. #r "nuget: Octopus.Client" using Octopus.Client;
• Support for net7.0
• net6.0 SDK requirement

This PR addresses some technical issues customers experienced during the attempted rollout. We are not addressing all of these issues.

References to Octopus.Client have been fixed however the Octopus class had to be removed from the C# Bootstrapper. This brings the C# scripting in line with Powershell, where calls like Octopus.SetVariable are now SetVariable and Octopus.Parameters are now OctopusParameters. This will have to be updated in the front end source code editor, and should reflect the environment variable toggle. This will also have to be documented.

This change still requires net6.0 on the deployment target, we can work around this using the Dotnet.Script Nuget package, copying across the program.cs and building self-contained versions of the project. This is ~160MB for the Windows build alone. This isn't a practical addition to Calamari considering the space taken. If customers cannot install net6.0 they can use the PowerShell ScriptCS workaround.

Similar to above we currently only support net6.0, this is due to the dotnet-tool bundle we include, which can be updated to include both net6.0 and net7.0, the size in this case isn't as much of an issue. However, we'd have to check the host dotnet version prior to execution, in initial discussions we'd like to avoid this. Feel free to push back on this point, it may be worth a more in-depth discussion. We'll need to keep this in mind for dotnet versioning in Calamari and dotnet-script this dependency isn't good.

This depends on the server changes in https://github.com/OctopusDeploy/OctopusDeploy/pull/21279
[sc-61383]

Comms:
OctopusDeploy/blog#1077
OctopusDeploy/docs#2035 - TBD on merging and calling out the multiple C# scripting engines for now.

Before merging this we will need to notify customers using the Dotnet Script functionality, I'll reach out to support in the dotnet-script channel.

After:

Scripts:

(TeamMembers updated for run)

Output:

Running on WSL and ubuntu containers in WSL

With Class based bootstrapper & dotnet-script:

No feature toggles running ScriptCS:

[shortcut-integration]

This pull request has been linked to Shortcut Story #61383: Dotnet-Script fixes.

[hnrkndrssn]

LGTM 👍

[IsaacCalligeros95]

LGTM 👍

I've updated this to include a toggle for the existing class-based bootstrapper. This is for a specific customer that has already migrated and will prevent failing deployments until they are ready to migrate.
Related Server PR - https://github.com/OctopusDeploy/OctopusDeploy/pull/21279

[hnrkndrssn]

👍