fix: update libdatadog references, set hostname to empty string for trace stats

[duncanpharvey]

What does this PR do?

• Update libdatadog references to latest commit
• Refactor trace flusher to rely on SendData for retries

Motivation

When hostname is sent on trace metrics it results in ephemeral instances from Azure Functions populating as hosts in the Infrastructure List.

https://datadoghq.atlassian.net/browse/SVLS-8520

Additional Notes

• libdatadog change needed for this: fix(serverless): set hostname on stats from tracer to empty string libdatadog#1530
• Due to a breaking change in libdatadog we need to refactor the trace flusher to not use libdd_trace_utils::send_data::SendData: std::clone::Clone. This was originally added for retrying failed trace flushes to Datadog but since retry logic was added to SendData since then we can remove it.
  • Breaking change in feat(sidecar)!: introduce TraceData to unify text and binary data libdatadog#1247
  • Retry logic added in Add retry logic to trace_utils::SendData libdatadog#433

error[E0599]: the method `clone` exists for struct `std::vec::Vec<libdd_trace_utils::send_data::SendData>`, but its trait bounds were not satisfied
   --> crates/datadog-trace-agent/src/trace_flusher.rs:105:35
    |
105 |         let traces_clone = traces.clone();
    |                                   ^^^^^
    |
   ::: /Users/duncan.harvey/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/vec/mod.rs:434:1
    |
434 | pub struct Vec<T, #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global> {
    | ------------------------------------------------------------------------------------------------ doesn't satisfy `_: Clone`
    |
   ::: /Users/duncan.harvey/.cargo/git/checkouts/libdatadog-fb268e227e330049/f97c41f/libdd-trace-utils/src/send_data/mod.rs:67:1
    |
 67 | pub struct SendData {
    | ------------------- doesn't satisfy `_: Clone`
    |
    = note: the following trait bounds were not satisfied:
            `libdd_trace_utils::send_data::SendData: std::clone::Clone`
            which is required by `std::vec::Vec<libdd_trace_utils::send_data::SendData>: std::clone::Clone`

Describe how to test/QA your changes

• Updated unit tests
• Deployed to Azure Functions and verified (1) hostname is none on any trace metrics, (2) hosts from ephemeral instances for Azure Functions age out of the Infrastructure List, and (3) traces continue to be sent successfully to Datadog.

[kathiehuang]

How did you realize retries are now handled internally by SendData?

[duncanpharvey]

I was reviewing the PR in libdatadog with the breaking change and noticed the send_with_retry method. feat(sidecar)!: introduce TraceData to unify text and binary data

Digging further I found that this retry logic was added some time ago in May 2024! I added a link to this PR in the description for additional context. Add retry logic to trace_utils::SendData