MEDIUM: tcpcheck: Use small buffer if possible for healthchecks

MEDIUM: tcpcheck: Use small buffer if possible for healthchecks

If support for small buffers is enabled, we now try to use them for
healthcheck requests. First, we take care the tcpcheck ruleset may use small
buffers. Send rules using LF strings or too large data are excluded. The
ability to use small buffers or not are set on the ruleset. All send rules
of the ruleset must be compatible. This info is then transfer to server's
healthchecks relying on this ruleset.

Then, when a healthcheck is running, when a send rule is evaluated, if
possible, we try to use small buffers. On error, the ability to use small
buffers is removed and we retry with a regular buffer. It means on the first
error, the support is disabled for the healthcheck and all other runs will
use regular buffers.