We previously waited for the initialization response from the build server during the creation of a `Workspace` so that we could create a `SemanticIndexManager` with the index store path etc. that was returned by the `build/initialize` response. This caused all functionality (including syntactic) of SourceKit-LSP to be blocked until the build server was initialized.
Change the computation of the `SemanticIndexManager` and related types to happen in the background so that we can provide functionality that doesn’t rely on the build server immediately.
Fixes#2304
The term *build system* predated our wide-spread adoption of BSP for communicating between SourceKit-LSP to the build system and was never really the correct term anyway – ie. a `JSONCompilationDatabaseBuildSystem` never really sounded right. We now have a correct term for the communication layer between SourceKit-LSP: A build server. Rename most occurrences of *build system* to *build server* to reflect this. There are unfortunately a couple lingering instances of *build system* that we can’t change, most notably: `fallbackBuildSystem` in the config file, the `workspace/waitForBuildSystemUpdates` BSP extension request and the `synchronize-for-build-system-updates` experimental feature.
