chore(deps): bump dd-trace-rs to datadog-opentelemetry-v0.5.0 (#144)

Bumps the datadog-opentelemetry git rev pinned by datadog-agent-config
from f51cefc4 (pre-v0.3.0) to 50bfea87 (v0.5.0). Regenerates Cargo.lock
and LICENSE-3rdparty.csv accordingly.

v0.5.0 adds native B3 (single and multi-header) trace propagation
support, which is needed to fix "Unknown trace propagation style:
'b3multi'" errors reported by customers using B3 propagation with the
Lambda extension.

This is a prerequisite for bumping dd-trace-rs in
DataDog/datadog-lambda-extension, whose own direct pin of
datadog-opentelemetry must stay in lockstep with this crate's pin
(datadog-agent-config re-exports datadog_opentelemetry::configuration::
TracePropagationStyle, so the two pins must resolve to the same
revision).

Verified: cargo check/clippy/fmt clean across the workspace,
datadog-agent-config's 79 unit tests pass, dd-rust-license-tool check
passes. Two pre-existing dogstatsd::flusher test failures are unrelated
(reproduce identically on unmodified main).

JIRA: https://datadoghq.atlassian.net/browse/SLES-2907

Author: litianningdatadog