Add additional trace2 regions for fetch and push

Last year at $DAYJOB we were having issues with slow fetches/pulls/pushes. We added some additional trace2 regions which helped us narrow down the issue to some server-side negotiation problems. We've been carrying these patches downstream ever since, but they might be useful to others as well.

Changes in V2:

* Added a new patch to implement trace2_printf() for event targets.

* Move some fetch trace regions deeper in the call stack to simplify control flow.

* Move some push trace regions deeper in the call stack to target the actual slow functions, and to not tie tracing to whether or not sideband communication is used.

Calvin Wan (1):
send-pack: add new tracing regions for push

Josh Steadmon (2):
trace2: implement trace2_printf() for event target
fetch: add top-level trace2 regions

 Documentation/technical/api-trace2.txt | 17 +++++++++++++++--
 builtin/fetch.c                        | 16 +++++++++++++++-
 bundle-uri.c                           |  4 ++++
 send-pack.c                            | 16 +++++++++++++---
 trace2/tr2_tgt_event.c                 | 22 ++++++++++++++++++++--
 5 files changed, 67 insertions(+), 8 deletions(-)

base-commit: 25673b1c476756ec0587fb0596ab3c22b96dc52a

2.46.0.295.g3b9ea8a38a-goog