lib: TLS session ticket caching reworked

Described in detail in internal doc TLS-SESSIONS.md

Main points:
- use a new `ssl_peer_key` for cache lookups by connection filters
- recognize differences between TLSv1.3 and other tickets
  * TLSv1.3 tickets are single-use, cache can hold several of them for a peer
  * TLSv1.2 are reused, keep only a single one per peer
- differentiate between ticket BLOB to store (that could be persisted) and object instances
- use put/take/return pattern for cache access
- remember TLS version, ALPN protocol, time received and lifetime of ticket
- auto-expire tickets after their lifetime

Closes #15774

lib/dynbuf.h

@@ -39,6 +39,7 @@
 #define Curl_dyn_uptr(a) curlx_dyn_uptr(a)
 #define Curl_dyn_len(a) curlx_dyn_len(a)
 #define Curl_dyn_reset(a) curlx_dyn_reset(a)
+#define Curl_dyn_take(a,b) curlx_dyn_take(a,b)
 #define Curl_dyn_tail(a,b) curlx_dyn_tail(a,b)
 #define Curl_dyn_setlen(a,b) curlx_dyn_setlen(a,b)
 #define curlx_dynbuf dynbuf /* for the struct name */
@@ -75,6 +76,10 @@ size_t Curl_dyn_len(const struct dynbuf *s);
 /* The implementation of this function exists in mprintf.c */
 int Curl_dyn_vprintf(struct dynbuf *dyn, const char *format, va_list ap_save);
 
+/* Take the buffer out of the dynbuf. Caller has ownership and
+ * dynbuf resets to initial state. */
+char *Curl_dyn_take(struct dynbuf *s, size_t *plen);
+
 /* Dynamic buffer max sizes */
 #define DYN_DOH_RESPONSE    3000
 #define DYN_DOH_CNAME       256