Changelog #208

#15891 diagnose some orphan trait impl cases:

#15895 diagnose missing associated items in trait impls:

#15893 diagnose incorrect unsafety for trait impls:

#15901 diagnose everything in nested items.

#15903 make line! and column! expand to literals.

#15875 fix PathSegment grammar.

#15899, #15917 sync from downstream.

#15874 migrate assists to the structured snippet API, part 4.

#15925 remove debugging code in path resolution.

#15902, #15913 bump some deps.

#15830 VS Code: expose workspaces to other extensions, remove addProject command.

#15900 disable VSIX builds for win32-ia32, which VS Code no longer supports.

#15904 bump minimum supported VS Code to 1.78.