Add Nextflow language server support (#1815)

The Nextflow language server schedules a debounced (1s) AST update on every
didOpen/didChange, and LanguageService.references is the only request that does
not await it -- documentSymbol, codeLens, documentLink and semanticTokensFull
all do. A references request issued inside that window races the recompile of
the file it asks about and can return an empty list, which is what the macOS CI
runner hit. Send a documentSymbol request for the same file first, which blocks
server-side until the pending update has been applied.

Also compare reference paths using the platform separator in the tests, since
relativePath is OS-native and the hardcoded forward slashes failed on Windows.

scripts/update_downloaded_dependency_hashes.py

@@ -1,9 +1,11 @@
 from sensai.util import logging
 
 from solidlsp.language_servers.eclipse_jdtls import EclipseJDTLS
+from solidlsp.language_servers.nextflow_language_server import NextflowLanguageServer
 from solidlsp.language_servers.kotlin_language_server import KotlinLanguageServer
 
 if __name__ == "__main__":
     logging.configure()
     EclipseJDTLS.DependencyProvider.update_dep_hashes()
+    NextflowLanguageServer.DependencyProvider.update_dep_hashes()
     KotlinLanguageServer.DependencyProvider.update_dep_hashes()