Fix ESP32 UART configuration for ESP-IDF >= 5.0

[tovam]

Include source_clk field in the uart_config_t struct for ESP-IDF >= 5.0 to address compatibility error.

The issue arises due to a missing source_clk field in the uart_config_t struct in uart_driver_create_port.
In versions prior to ESP-IDF 5.0, this field was not required (tested against 4.4.6), but its absence in later versions leads to the following error at runtime : uart: uart_param_config(748): Invalid src_clk.
The choice of UART_SCLK_DEFAULT was made to allow for automatic selection of the appropriate clock source.

Open to feedback or suggestions for any improvements or alternative approaches.

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

[bettio]

Looks good. Let's add an entry to the changelog CHANGELOG.md file and we can merge it.

Something like "Fixed invalid src_clk error on ESP-IDF >= 5.0" or something like that, under the Fixed section for [0.6.0-alpha.2]

Please, add this entry to the changelog by just amending your commit (so we can keep the git history clean).

[tovam]

Great, done