ISB name is hardcoded in the generic reader.rs

[vigith]

There are places where we leak the ISB into the metric names.

numaflow/rust/numaflow-core/src/pipeline/isb/reader.rs

Lines 120 to 125 in 9dad6d9

	pipeline_metrics()
	.jetstream_isb
	.read_time_total
	.get_or_create(&jetstream_isb_metrics_labels(self.stream.name))
	.observe(start.elapsed().as_micros() as f64);