Lock free audio

[LeonidGoltsblat]

1. The main idea of ​​this PR is to create file players/recorders without locking. These operations take a lot of time because they call file io under a global lock and thus interfere with the processing of other calls. This type of load is especially typical for IVR-type applications. To avoid blocking, a slot reservation algorithm based on the new pj_stack data structure (see stack implementation and tests #4116) is used, which eliminates the need for PJSUA_LOCK() based lock protection on the pjsua_var.player[], pjsua_var.recorder[] arrays.
2. Fixed unnecessary locking in pjsua_conf_connect2() for typical server-side use (master port, conference bridge, no sound device). In this case, pjsua_conf_connect2() called PJSUA_LOCK() (waiting for others to unlock it and preventing other calls from being processed) but nothing happens within that lock.
3. Memory usage optimization: Immediately destroy temporary pools used to create file players/recorders. Currently, these pools are only used in the legacy conference switch, not in the conference bridge.
4. Introduced PJSUA_MASTER_PORT_OPTIONS macro to set pjmedia_master_port_create() options parameter. Before this PR we had the parameter but no way to set its value.

PS only 3 files are changed here:

• pjmedia/include/pjmedia/config.h
• pjsip/include/pjsua-lib/pjsua_internal.h
• pjsip/src/pjsua-lib/pjsua_aud.c
  Additional changes are inherited from stack implementation and tests #4116.