Survey of functions returning `bool` under workspace `gstreamer-sdp`

This is the last part of an overall effort throughout gstreamer-rs, which started with discussions in #166 (closed) & !196 (closed) (closed) and continued with several merge requests.

Basically, all functions which, from their name, were not obviously returning a boolean are candidate for switching to Result<(), glib::BoolError>.

Function	Location	Gst Function	Proposed Return Type	Comment
MikeyMessage.add_cs_srtp	auto	gst_mikey_message_add_cs_srtp	Result<(), glib::BoolError>	Add a Crypto policy for SRTP to msg. Returns TRUE on success
MikeyMessage.add_payload	src	gst_mikey_message_add_payload	Result<(), glib::BoolError>	Add a new payload to msg. Returns TRUE on success
MikeyMessage.add_pke	auto	gst_mikey_message_add_pke	Result<(), glib::BoolError>	Add a new PKE payload to msg with the given parameters. Returns TRUE on success
MikeyMessage.add_rand	auto	gst_mikey_message_add_rand	Result<(), glib::BoolError>	Add a new RAND payload to msg with the given parameters. Returns TRUE on success
MikeyMessage.add_rand_len	auto	gst_mikey_message_add_rand_len	Result<(), glib::BoolError>	Add a new RAND payload to msg with len random bytes. Returns TRUE on success
MikeyMessage.add_t	src	gst_mikey_message_add_t	Result<(), glib::BoolError>	Add a new T payload to msg with the given parameters. Returns TRUE on success
MikeyMessage.add_t_now_ntp_utc	auto	gst_mikey_message_add_t_now_ntp_utc	Result<(), glib::BoolError>	Add a new T payload to msg that contains the current time in NTP-UTC format. Returns TRUE on success
MikeyMessage.insert_cs_srtp	src	gst_mikey_message_insert_cs_srtp	Result<(), glib::BoolError>	Insert a Crypto Session map for SRTP in msg at idx. Returns TRUE on success
MikeyMessage.insert_payload	src	gst_mikey_message_insert_payload	Result<(), glib::BoolError>	Insert the payload at index idx in msg. Returns TRUE on success
MikeyMessage.remove_cs_srtp	auto	gst_mikey_message_remove_cs_srtp	Result<(), glib::BoolError>	Remove the SRTP policy at idx. Returns TRUE on success
MikeyMessage.remove_payload	auto	gst_mikey_message_remove_payload	Result<(), glib::BoolError>	Remove the payload in msg at idx. Returns TRUE on success
MikeyMessage.replace_cs_srtp	src	gst_mikey_message_replace_cs_srtp	Result<(), glib::BoolError>	Replace a Crypto Session map for SRTP in msg at idx with map. Returns TRUE on success
MikeyMessage.replace_payload	src	gst_mikey_message_replace_payload	Result<(), glib::BoolError>	Replace the payload at idx in msg with payload. Returns TRUE on success
MikeyMessage.set_info	auto	gst_mikey_message_set_info	Result<(), glib::BoolError>	Set the information in msg. Returns TRUE on success
MikeyMessage.to_caps	auto	gst_mikey_message_to_caps	Result<(), glib::BoolError>	(fills caps with SRTP parameters). Returns TRUE on success
MikeyPayload.kemac_add_sub	src	gst_mikey_payload_kemac_add_sub	Result<(), glib::BoolError>	Add a new sub payload to payload. Returns TRUE on success
MikeyPayload.kemac_remove_sub	auto	gst_mikey_payload_kemac_remove_sub	Result<(), glib::BoolError>	Remove the sub payload at idx in payload. Returns TRUE on success
MikeyPayload.kemac_set	auto	gst_mikey_payload_kemac_set	Result<(), glib::BoolError>	Set the KEMAC parameters. Returns TRUE on success
MikeyPayload.key_data_set_interval	src	gst_mikey_payload_key_data_set_interval	Result<(), glib::BoolError>	Set the key validity period in the GST_MIKEY_PT_KEY_DATA payload. Returns TRUE on success
MikeyPayload.key_data_set_key	auto	gst_mikey_payload_key_data_set_key	Result<(), glib::BoolError>	Set key_len bytes of key_data of type key_type as the key for the GST_MIKEY_PT_KEY_DATA payload. Returns TRUE on success
MikeyPayload.key_data_set_salt	auto	gst_mikey_payload_key_data_set_salt	Result<(), glib::BoolError>	Set the salt key data. Returns TRUE on success
MikeyPayload.key_data_set_spi	auto	gst_mikey_payload_key_data_set_spi	Result<(), glib::BoolError>	Set the SPI/MKI validity in the GST_MIKEY_PT_KEY_DATA payload. Returns TRUE on success
MikeyPayload.pke_set	auto	gst_mikey_payload_pke_set	Result<(), glib::BoolError>	Set the PKE values in payload. payload must be of type GST_MIKEY_PT_PKE. Returns TRUE on success
MikeyPayload.rand_set	auto	gst_mikey_payload_rand_set	Result<(), glib::BoolError>	Set the random values in a GST_MIKEY_PT_RAND payload. Returns TRUE on success
MikeyPayload.sp_add_param	auto	gst_mikey_payload_sp_add_param	Result<(), glib::BoolError>	Add a new parameter to the GST_MIKEY_PT_SP payload with type , len and val. Returns TRUE on success
MikeyPayload.sp_remove_param	auto	gst_mikey_payload_sp_remove_param	Result<(), glib::BoolError>	Remove the Security Policy parameters from a GST_MIKEY_PT_SP payload at idx. Returns TRUE on success
MikeyPayload.sp_set	auto	gst_mikey_payload_sp_set	Result<(), glib::BoolError>	Set the Security Policy parameters for payload. Returns TRUE on success
MikeyPayload.t_set	src	gst_mikey_payload_t_set	Result<(), glib::BoolError>	Set the timestamp in a GST_MIKEY_PT_T payload. Returns TRUE on success