[gRPC]: Fix oob access of string_view in example

[Tradias]

The GrpcClient/ServerCarrier in the gRPC examples assume that the provided string_views are null-terminated,
which is not necessarily the case, e.g. when they are provided by the HttpTraceContext:

opentelemetry-cpp/api/include/opentelemetry/trace/propagation/http_trace_context.h

Lines 89 to 102 in 82a8115

	char trace_parent[kTraceParentSize];
	trace_parent[0] = '0';
	trace_parent[1] = '0';
	trace_parent[2] = '-';
	span_context.trace_id().ToLowerBase16(
	nostd::span<char, 2 * TraceId::kSize>{&trace_parent[3], kTraceIdSize});
	trace_parent[kTraceIdSize + 3] = '-';
	span_context.span_id().ToLowerBase16(
	nostd::span<char, 2 * SpanId::kSize>{&trace_parent[kTraceIdSize + 4], kSpanIdSize});
	trace_parent[kTraceIdSize + kSpanIdSize + 4] = '-';
	span_context.trace_flags().ToLowerBase16(
	nostd::span<char, 2>{&trace_parent[kTraceIdSize + kSpanIdSize + 5], 2});
	carrier.Set(kTraceParent, nostd::string_view(trace_parent, sizeof(trace_parent)));

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Tradias / name: Dennis (b8758ca)

[codecov]

Codecov Report

Merging #1619 (b8758ca) into main (82a8115) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1619   +/-   ##
=======================================
  Coverage   85.24%   85.24%           
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  Files         156      156           
  Lines        4978     4978           
=======================================
  Hits         4243     4243           
  Misses        735      735           

[owent]

LGTM