Unify licence headers across UMF

[lplewa]

There is two different license header in tests - it should be unified.

[bratpiorka]

/*
 *
 * Copyright (C) 2023 Intel Corporation
 *
 * Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 */

vs

// Copyright (C) 2023-2024 Intel Corporation
// Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

@igchor @vinser52 ?

[lukaszstolarczuk]

I think in previous projects we mostly used:

// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2015-2019, Intel Corporation */

Sometimes, we used a sligthly different version for header files:

/* SPDX-License-Identifier: BSD-3-Clause */
/* Copyright 2015-2020, Intel Corporation */

[ldorau]

I cannot find a link to the Intel guide/wiki, but according to Intel guidelines it should be exactly like in the https://github.com/pmem/pmdk project (do not ask me why ;-)), so:

1. in the source files:

// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2014-2023, Intel Corporation */

2. in the header files:

/* SPDX-License-Identifier: BSD-3-Clause */
/* Copyright 2014-2021, Intel Corporation */

[bratpiorka]

we should also add all licenses we use to LICENSE.TXT