MEDIUM: ech: implement a lighter ECH feature for AWS-LC

MEDIUM: ech: implement a lighter ECH feature for AWS-LC

This patch implements ECH with AWS-LC. AWS-LC supports a different ECH
API than OpenSSL 4.0.

AWS-LC does not implement an API to load a PEM ECH file, the ECHCONFIG
section is parsed manually using PEM_read_bio() to feed the SSL_ECH_KEYS
object.

Runtime ECH store management ('show/add/set/del ssl ech') and ECH
status/outer-SNI reporting  are disabled under AWS-LC for now.

Should fix issue #3333.