entity-manager: constructor arg to load config

Introduce a constructor arg to point EM to directories to load
configuration from.

This enables running unit tests without depending on a specific
directory layout from our rofs.

Tested: on Tyan S8030. Config parsed as expected.

```
Oct 02 11:22:52 s8030-bmc-30303035c0c1 systemd[1]: Starting Entity Manager...
Oct 02 11:22:52 s8030-bmc-30303035c0c1 systemd[1]: Started Entity Manager.
Oct 02 11:23:02 s8030-bmc-30303035c0c1 entity-manager[8265]: There's still template variable $PRODUCT_PART_NUMBER un-replaced. Removing it from the string.
Oct 02 11:23:02 s8030-bmc-30303035c0c1 entity-manager[8265]: There's still template variable $PRODUCT_ASSET_TAG un-replaced. Removing it from the string.
Oct 02 11:23:02 s8030-bmc-30303035c0c1 entity-manager[8265]: There's still template variable $PRODUCT_ASSET_TAG un-replaced. Removing it from the string.
Oct 02 11:23:02 s8030-bmc-30303035c0c1 entity-manager[8265]: There's still template variable $PRODUCT_ASSET_TAG un-replaced. Removing it from the string.
Oct 02 11:23:02 s8030-bmc-30303035c0c1 entity-manager[8265]: There's still template variable $PRODUCT_PART_NUMBER un-replaced. Removing it from the string.
Oct 02 11:23:04 s8030-bmc-30303035c0c1 entity-manager[8265]: Inventory Added: Supermicro PWS 920P SQ 0
Oct 02 11:23:04 s8030-bmc-30303035c0c1 entity-manager[8265]: Inventory Added: Supermicro PWS 920P SQ 1
Oct 02 11:23:04 s8030-bmc-30303035c0c1 entity-manager[8265]: Inventory Added: Tyan S8030 Baseboard
Oct 02 11:23:04 s8030-bmc-30303035c0c1 entity-manager[8265]: Inventory Added: MBX 1.57 Chassis
```

Change-Id: I8ce297847d3cafe2e2ae2040e9db261dc1d8f426
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/src/entity_manager/entity_manager.hpp b/src/entity_manager/entity_manager.hpp
index 33efb31..c21b94e 100644
--- a/src/entity_manager/entity_manager.hpp
+++ b/src/entity_manager/entity_manager.hpp
@@ -20,7 +20,8 @@
   public:
     explicit EntityManager(
         std::shared_ptr<sdbusplus::asio::connection>& systemBus,
-        boost::asio::io_context& io);
+        boost::asio::io_context& io,
+        const std::vector<std::filesystem::path>& configurationDirectories);
 
     // disable copy
     EntityManager(const EntityManager&) = delete;