[core] Modularize FileSource codebase (#15768)

* [core] Introduce FileSourceManager and use it for default platform impl

  - Add `FileSourceManager` interface that provides access to `FileSource`
    instances and means of registering / unregistering `FileSource` factories
  - Split `DefaultFileSource` into smaller parts
  - Add `DatabaseFileSource` interface and it's default implementation
  - Remove inter-dependencies between concrete `FileSource` classes

* [build] Add files to next build system

* [core] Add generic property setters / getters

* [core] Remove setOnlineStatus from OnlineFileSource interface

* [core] Hide threading implementation details from DatabaseFileSource interface

* [core] Make DB file source methods virtual

* [core] Add documentation for DatabaseFileSource and rename one method

* [core] Use simple callback instead of ActorRef

* [core] Remove ActorRef from OnlineFileSource public header

* [core] Add callback to FileSource::forward async API

* [core] Pass OfflineRegionDefinition by value

* [core] Update tests to use modular file sources

* [core] Update unit tests

* [core] Update unit tests after rebase

* [core] Backport low prio fix for cached requests

* [core] Backport pack database

* [core] Return removed factory from unRegisterFileSourceFactory

* [core] Rename shadowed args in onlinefilesource

* [core] Remove simple std::function callback aliases

* [core] Expose online file source property keys in public header file

* [test-runner] Add proxy file source test runner

* [cache] Update mbgl-cache utility to use new file source

* [metrics] Rebaseline binary size metrics

* [offline] Update offline utility

* [core] Update changelog

3 files changed, 7 insertions, 7 deletions

diff --git a/test/style/source.test.cpp b/test/style/source.test.cpp
index 5eb837d92b..0286aaaec3 100644
--- a/test/style/source.test.cpp
+++ b/test/style/source.test.cpp
@@ -58,7 +58,7 @@ public:
     StubRenderSourceObserver renderSourceObserver;
     Transform transform;
     TransformState transformState;
-    Style style { *fileSource, 1 };
+    Style style{fileSource, 1};
     AnnotationManager annotationManager { style };
     ImageManager imageManager;
     GlyphManager glyphManager;
diff --git a/test/style/style.test.cpp b/test/style/style.test.cpp
index b9e19d5a85..c866431ac1 100644
--- a/test/style/style.test.cpp
+++ b/test/style/style.test.cpp
@@ -18,7 +18,7 @@ using namespace mbgl::style;
 TEST(Style, Properties) {
     util::RunLoop loop;
 
-    StubFileSource fileSource;
+    auto fileSource = std::make_shared<StubFileSource>();
     Style::Impl style { fileSource, 1.0 };
 
     style.loadJSON(R"STYLE({"name": "Test"})STYLE");
@@ -60,7 +60,7 @@ TEST(Style, Properties) {
 TEST(Style, DuplicateSource) {
     util::RunLoop loop;
 
-    StubFileSource fileSource;
+    auto fileSource = std::make_shared<StubFileSource>();
     Style::Impl style { fileSource, 1.0 };
 
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));
@@ -81,7 +81,7 @@ TEST(Style, RemoveSourceInUse) {
     auto log = new FixtureLogObserver();
     Log::setObserver(std::unique_ptr<Log::Observer>(log));
 
-    StubFileSource fileSource;
+    auto fileSource = std::make_shared<StubFileSource>();
     Style::Impl style { fileSource, 1.0 };
 
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));
@@ -106,7 +106,7 @@ TEST(Style, RemoveSourceInUse) {
 
 TEST(Style, SourceImplsOrder) {
     util::RunLoop loop;
-    StubFileSource fileSource;
+    auto fileSource = std::make_shared<StubFileSource>();
     Style::Impl style{fileSource, 1.0};
 
     style.addSource(std::make_unique<VectorSource>("c", "mapbox://mapbox.mapbox-terrain-v2"));
diff --git a/test/style/style_layer.test.cpp b/test/style/style_layer.test.cpp
index 1d60197c2d..77e936ff3b 100644
--- a/test/style/style_layer.test.cpp
+++ b/test/style/style_layer.test.cpp
@@ -283,7 +283,7 @@ TEST(Layer, DuplicateLayer) {
     util::RunLoop loop;
 
     // Setup style
-    StubFileSource fileSource;
+    auto fileSource = std::make_shared<StubFileSource>();
     Style::Impl style { fileSource, 1.0 };
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));
 
@@ -304,7 +304,7 @@ TEST(Layer, IncompatibleLayer) {
     util::RunLoop loop;
 
     // Setup style
-    StubFileSource fileSource;
+    auto fileSource = std::make_shared<StubFileSource>();
     Style::Impl style{fileSource, 1.0};
     style.loadJSON(util::read_file("test/fixtures/resources/style-unused-sources.json"));