esp_modem: esp_modem_set_echo is not defined (IDFGH-16699)

[maksz42]

Answers checklist.

• I have read the documentation for esp-protocols components and the issue is not addressed there.
• I have updated my esp-protocols branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

General issue report

The esp_modem C API declares esp_modem_set_echo, but there is no definition.

esp-protocols/components/esp_modem/command/include/esp_modem_api.h

Lines 64 to 69 in 732cd29

	/**
	* @brief Sets echo mode
	* @param[in] echo_on true if echo mode on (repeats the commands)
	* @return OK, FAIL or TIMEOUT
	*/
	esp_err_t esp_modem_set_echo(esp_modem_dce_t *dce, const bool echo_on);