chore(deps): consolidated dependency updates (supersedes 5 dependabot PRs)

[mivano]

Bumps all outdated NuGet dependencies in one go:

Package	From	To
Microsoft.Extensions.DependencyInjection (src + tests)	10.0.11	10.0.12
Microsoft.Extensions.Http.Polly	10.0.11	10.0.12
Microsoft.SourceLink.GitHub	10.0.300	10.0.401
Polly	8.7.0	8.8.0
Microsoft.NET.Test.Sdk	18.9.0	18.10.1
xunit.runner.visualstudio	3.1.5	4.0.0
coverlet.collector / coverlet.msbuild	10.0.1	10.1.0
Moq	4.20.72	4.21.0

Notes:

• Bump Microsoft.Extensions.Http.Polly from 10.0.11 to 10.0.12 #356 failed CI on its own with NU1605 because Http.Polly 10.0.12 requires DI >= 10.0.12; bumping both together resolves it.
• The SourceLink bump clears the NU1902 advisory on Microsoft.Build.Tasks.Git 10.0.300.
• Also picks up Polly, coverlet and Moq updates that had no Dependabot PR yet.

Supersedes #352, #355, #356, #357, #358.

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