New command-line APIs in sourcelink

[NikolaMilosavljevic]

Patch for dotnet/sourcelink#1068

This brings the following changes to sourcelink global tool, that enable sourcelink tests in source-build:

• Adds --offline argument for test option - enables test option in offline scenarios
• Fixes Make dotnet-sourcelink source-buildable sourcelink#1028 - enables tool to be built in source-build
• Updates command-line-api dependency to match what's used in source-build, and all other repos that have that dependency
• Converts command-line usage to new API model, as required by updated command-line-api dependency - same work that was recently done in other repos, i.e. dotnet/sdk@6483a69

[NikolaMilosavljevic]

Source-build failure - VMR could not apply the patch - working on updating the patch.