#What does this PR do?

Bumps the libdatadog workspace version from 34.0.0 → 35.0.0 (Cargo.toml + regenerated Cargo.lock) to cut the 35.0.0 release.

Breaking changes affecting the FFI layer (34.0.0 → 35.0.0)

1. Tracer FFI: response body now returned as ByteSlice (feat!: Align tracer FFI error and response types with common conventions #2029) — feat!

• ddog_trace_exporter_response_get_body no longer takes an out_len: *mut usize out-parameter and returns *const u8. It now returns a single ByteSlice value, matching the slice
  conventions in libdd-common-ffi.
• Tracer constructor functions now validate nullable pointers and return ErrorCode::InvalidArgument instead of risking UB; panics across the boundary are caught and surfaced as
  ErrorCode::Panic.
• C consumers (e.g. dd-trace-rb) can now reuse the standard read_ddogerr_string_and_drop / get_error_details_and_drop helpers from datadog_ruby_common.h.
• Action for callers: drop the out_len argument and read length/pointer from the returned ByteSlice.

2. Crashtracker: error.threads flattened to []ThreadData (fix(crashtracking)!: flatten all threads object into a list of ThreadData #2054) — fix(crashtracking)!

• The crash-report payload now emits error.threads as an optional flat array of thread objects (unified runtime stack schema 1.8) instead of the previous nested threads object.
• This is a wire/payload-format change consumed by downstream pipelines and the product UI.
• Action for callers: consumers parsing crash reports must update to the 1.8 thread layout.

Other breaking changes since 34.0.0 (Rust API, not C ABI)

These are !-marked breaking changes in libdd-trace-utils that affect Rust consumers of the library but do not change the C FFI surface or generated headers:

• feat(trace-utils)!: introduce VecMap datastructure (feat(trace-utils)!: introduce VecMap datastructure #2022) — adds a HashMap replacement optimized for span construction (not yet wired into span fields).
• feat(trace-utils)!: add from_string to span text (feat(trace-utils)!: add from_string to span text #2011) — requires From on SpanText and switches SpanSlice to Cow to allow span-field mutation/normalization.

Notable new FFI surface (additive)

• feat: Add FFI for trace exporter (feat: Add FFI for trace exporter #1952) — new tracer FFI surface in libdd-data-pipeline-ffi (the change above, feat!: Align tracer FFI error and response types with common conventions #2029, refines it).