Include pod UID and container name as optional trace labels

[sfleen]

It's useful to include these fields in the trace span attributes to help correlate traffic within a cluster.

This propagates these labels through the trace initialization, similar to how we handle the service name (and other labels that last for the entire pod lifetime).

See linkerd/linkerd2#13501 for the corresponding control plane change.

[cratelyn]

you've been clippy'ed 📎 🙀

Error: error: this function has too many arguments (8/7)
  --> linkerd/app/src/trace_collector/otel_collector.rs:21:1
   |
21 | / pub(super) fn create_collector<S>(
22 | |     addr: ControlAddr,
23 | |     hostname: Option<String>,
24 | |     pod_uid: Option<String>,
...  |
29 | |     legacy_metrics: metrics::Registry,
30 | | ) -> EnabledCollector
   | |_____________________^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#too_many_arguments
   = note: `-D clippy::too-many-arguments` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::too_many_arguments)]`

[cratelyn]

besides the note about clippy lints above, this looks like a good PR to me. this should be a nice improvement to our traces!

[codecov]

Codecov Report

Attention: Patch coverage is 5.00000% with 19 lines in your changes missing coverage. Please review.

Project coverage is 66.59%. Comparing base (96124bc) to head (2a8c4e4).
Report is 768 commits behind head on main.

Files with missing lines	Patch %	Lines
linkerd/app/src/trace_collector/otel_collector.rs	0.00%	7 Missing ⚠️
linkerd/app/src/trace_collector.rs	0.00%	6 Missing ⚠️
linkerd/app/src/env.rs	20.00%	4 Missing ⚠️
linkerd/app/src/env/trace.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3483      +/-   ##
==========================================
- Coverage   67.68%   66.59%   -1.09%     
==========================================
  Files         332      390      +58     
  Lines       15158    18340    +3182     
==========================================
+ Hits        10259    12214    +1955     
- Misses       4899     6126    +1227     

Files with missing lines	Coverage Δ
linkerd/app/src/env/trace.rs	46.66% <0.00%> (ø)
linkerd/app/src/env.rs	52.73% <20.00%> (-6.67%)	⬇️
linkerd/app/src/trace_collector.rs	26.47% <0.00%> (ø)
linkerd/app/src/trace_collector/otel_collector.rs	0.00% <0.00%> (ø)

... and 172 files with indirect coverage changes

---

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