Configure diagnostics (and MapLibre) using Pkl. (#3820)

* Bump the version for the next release.

* Ignore all generated sources.

* Use Pkl+XcodeGen to inject secrets instead of the project.

* Inject the PostHog/Sentry/Rageshake configuration from the environment.

* Fix bad unicode.

* Fix unit tests.

ElementX/SupportingFiles/target.yml

@@ -42,10 +42,6 @@ targets:
     type: application
     platform: iOS
 
-    configFiles:
-      Debug: ../SupportingFiles/secrets.xcconfig
-      Release: ../SupportingFiles/secrets.xcconfig
-
     info:
       path: ../SupportingFiles/Info.plist
       properties:
@@ -109,8 +105,6 @@ targets:
           LSHandlerRank: Owner
           LSItemContentTypes: $(PILLS_UT_TYPE_IDENTIFIER)
         LSSupportsOpeningDocumentsInPlace: false
-        mapLibreAPIKey: $(MAPLIBRE_API_KEY)
-
 
     settings:
       base:
@@ -226,6 +220,7 @@ targets:
       excludes:
         - Other/Extensions/XCTestCase.swift
         - Other/Extensions/XCUIElement.swift
+    - path: ../../Secrets/Secrets.swift
     - path: ../Resources
     - path: ../SupportingFiles
     - path: ../../Tools/Scripts/Templates/SimpleScreenExample/ElementX