build: add headers needed in Conan package for libxrpl (#4885)

These headers are required in the xrpl Conan package in order for
xbridge witness server (xbwd) to build. This change to libxrpl may help
any dependents of libxrpl. This addition does not change any C++ code.

Builds/CMake/RippledCore.cmake

@@ -230,6 +230,11 @@ install (
   FILES
     src/ripple/json/impl/json_assert.h
   DESTINATION include/ripple/json/impl)
+
+install (
+    FILES
+      src/ripple/net/RPCErr.h
+    DESTINATION include/ripple/net)
 install (
   FILES
     src/ripple/protocol/AccountID.h
@@ -302,7 +307,35 @@ install (
     src/ripple/protocol/impl/STVar.h
     src/ripple/protocol/impl/secp256k1.h
   DESTINATION include/ripple/protocol/impl)
-
+install (
+    FILES
+      src/ripple/resource/Fees.h
+      src/ripple/resource/Charge.h
+    DESTINATION include/ripple/resource)
+install (
+  FILES
+    src/ripple/server/Port.h
+    src/ripple/server/Server.h
+    src/ripple/server/Session.h
+    src/ripple/server/SimpleWriter.h
+    src/ripple/server/Writer.h
+    src/ripple/server/WSSession.h
+    src/ripple/server/Handoff.h
+  DESTINATION include/ripple/server)
+install (
+  FILES
+    src/ripple/server/impl/ServerImpl.h
+    src/ripple/server/impl/io_list.h
+    src/ripple/server/impl/Door.h
+    src/ripple/server/impl/PlainHTTPPeer.h
+    src/ripple/server/impl/PlainWSPeer.h
+    src/ripple/server/impl/BaseHTTPPeer.h
+    src/ripple/server/impl/BaseWSPeer.h
+    src/ripple/server/impl/BasePeer.h
+    src/ripple/server/impl/LowestLayer.h
+    src/ripple/server/impl/SSLHTTPPeer.h
+    src/ripple/server/impl/SSLWSPeer.h
+  DESTINATION include/ripple/server/impl)
 #[===================================[
    beast/legacy headers installation
 #]===================================]
@@ -369,6 +402,7 @@ install (
     src/ripple/beast/utility/PropertyStream.h
     src/ripple/beast/utility/Zero.h
     src/ripple/beast/utility/rngfill.h
+    src/ripple/beast/utility/WrappedSink.h
   DESTINATION include/ripple/beast/utility)
 # WARNING!! -- horrible levelization ahead
 # (these files should be isolated or moved...but