feat(datasource): rename dotnet to `dotnet-version` (#20244)

lib/config/migrations/custom/datasource-migration.spec.ts

lib/config/migrations/custom/datasource-migration.ts

...fig/migrations/custom/match-datasources-migration.spec.ts

lib/config/migrations/custom/match-datasources-migration.ts

lib/config/migrations/migrations-service.ts

lib/modules/datasource/api.ts

.../datasource/dotnet-version/__fixtures__/releases-3.1.json

.../datasource/dotnet-version/__fixtures__/releases-5.0.json

.../datasource/dotnet-version/__fixtures__/releases-6.0.json

.../datasource/dotnet-version/__fixtures__/releases-7.0.json

...atasource/dotnet-version/__fixtures__/releases-index.json

lib/modules/datasource/dotnet-version/index.spec.ts

lib/modules/datasource/dotnet-version/index.ts

lib/modules/datasource/dotnet-version/readme.md

lib/modules/datasource/dotnet-version/schema.ts

lib/modules/manager/nuget/extract.spec.ts

lib/modules/manager/nuget/extract/global-manifest.ts

lib/modules/manager/nuget/index.ts