Relaunch UniGetUI through /bin/sh instead of powershell.exe off Windows - #5418

Member 'CancelAllOperations' does not access instance data and can be marked as static (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1822)

Member 'ClearFinishedOperations' does not access instance data and can be marked as static (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1822)

Member 'ClearSuccessfulOperations' does not access instance data and can be marked as static (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1822)

Member 'RetryFailedOperations' does not access instance data and can be marked as static (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1822)

Use 'string.Contains' instead of 'string.IndexOf' to improve readability (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2249)

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.