Make profile export a table function

[dentiny]

Is your feature request related to a problem? Please describe.

duckdb-filesystem-observability/src/observefs_extension.cpp

Lines 39 to 53 in 4af6cec

	static void GetProfileStats(const DataChunk &args, ExpressionState &state, Vector &result) {
	string latest_stat;
	const auto &observefs_instances = ObservabilityFsRefRegistry::Get().GetAllObservabilityFs();
	for (auto *cur_filesystem : observefs_instances) {
	latest_stat += StringUtil::Format("Current filesystem: %s\n", cur_filesystem->GetName());
	const auto cur_stats_str = cur_filesystem->GetHumanReadableStats();
	if (cur_stats_str.empty()) {
	latest_stat += "No interested IO operations issued.";
	} else {
	latest_stat += cur_stats_str;
	}
	latest_stat += "\n";
	}
	result.Reference(Value(std::move(latest_stat)));
	}

Current implementation is a scalar function, which exports everything into one cell;
a better approach is to export in table function.

Describe the solution you'd like
Refactor scalar function into table function.

Describe alternatives you've considered
N/A

Additional context
N/A