repo_transaction_stats: move to a manual implementation

This moves `RepoTransactionStats` into a manually implemented
source file in order to provide getters to expose relevant
fields.

rust-bindings/rust/conf/ostree.toml

@@ -89,6 +89,7 @@ manual = [
     "OSTree.KernelArgs",
     "OSTree.RepoCheckoutAtOptions",
     "OSTree.RepoCheckoutFilter",
+    "OSTree.RepoTransactionStats",
     "OSTree.SysrootWriteDeploymentsOpts",
     "OSTree.SysrootDeployTreeOpts",
 ]
@@ -187,12 +188,6 @@ status = "generate"
     name = "dup"
     ignore = true
 
-[[object]]
-name = "OSTree.RepoTransactionStats"
-status = "generate"
-init_function_expression = "|_ptr| ()"
-clear_function_expression = "|_ptr| ()"
-
 [[object]]
 name = "OSTree.SePolicy"
 status = "generate"