cmake: Copy cov_tool_wrapper.sh.in to the build tree

This change ensures that `cov_tool_wrapper.sh.in` is available when
invoking the `Coverage.cmake` script from any directory.

cmake/script/cov_tool_wrapper.sh.in

@@ -0,0 +1,5 @@
+# Copyright (c) 2024-present The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://opensource.org/license/mit/.
+
+exec @COV_TOOL@ "$@"