common/tracer: fix decoding when jaeger tracing is disabled

common/tracer: fix decoding when jaeger tracing is disabled

We aren't currently using jaeger tracing on Windows. The issue is
that Windows hosts (or any other host that doesn't use jaeger)
are experiencing message decoding failures after a recent change [1].

This change updates the tracer encoding so that messages from
non-jaeger hosts may be decoded by services that use jaeger.

[1] https://github.com/ceph/ceph/pull/47457

Signed-off-by: Lucian Petrut <lpetrut@cloudbasesolutions.com>
This commit rebrings 3701ffa6733b001d4278a0b68395c5efe2382f25 which
got reverted due to an implicit dependency with other revert. Please
see https://github.com/ceph/ceph/pull/52114#issuecomment-1950288188.

Conflicts:
	src/common/tracer.h
	  formatting conflict with 7179ac0037320480f089e1a9e291cdc37282d250

(cherry picked from commit e1452649b8e765e5ab1efdd71fe1d15461b6ef14)