CodeAction Handlers should use Server-side known Diagnostics

[fendor]

In #4056, it was established that HLS should not rely on the Diagnostics provided by the client to compute possible CodeActions.

Since then, we have introduced the functions activeDiagnosticsInRangeMT and activeDiagnosticsInRange in ghcide/src/Development/IDE/Core/PluginUtils.hs and use it in some locations.

The next step is to review all occurrences of mkPluginHandler SMethod_TextDocumentCodeAction and make sure we use these instead of the Diagnostics provided by the client.

So the task is to review such handlers, use activeDiagnosticsInRangeMT or activeDiagnosticsInRange respectively and then make sure the tests still pass, as lsp-test sometimes does something weird with source ranges, leading unexpected changes in the tests.

[fendor]

Ideally, we come up with some API or API changes to the plugin handlers that allow us to omit the step of manually calling activeDiagnosticsInRange* and automatically do the right thing... But I don't know right away how.