MINOR: ssl/ech: add logging and sample fetches for ECH status and outer SNI

MINOR: ssl/ech: add logging and sample fetches for ECH status and outer SNI

This patch adds functions to expose Encrypted Client Hello (ECH) status
and outer SNI information for logging and sample fetching.

Two new helper functions are introduced in ech.c:
 - conn_get_ech_status() places the ECH processing status string into a
   buffer.
 - conn_get_ech_outer_sni() retrieves the outer SNI value if ECH
   succeeded.

Two new sample fetch keywords are added:
 - "ssl_fc_ech_status" returns the ECH status string.
 - "ssl_fc_ech_outer_sni" returns the outer SNI value seen during ECH.

These allow ECH information to be used in HAProxy logs, ACLs, and
captures.