perf(sdk): store InstrumentationScope in Arc for cheaper tracer clones #11071

Job	Run time
docs	1m 47s
build-examples	1m 35s
msrv (ubuntu-latest)	3m 32s
lint	7m 0s
cargo-deny	1m 13s
coverage	2m 31s
msrv (windows-latest)	6m 32s
external-types (opentelemetry-otlp)	1m 16s
test (stable, ubuntu-24.04-arm)	4m 3s
external-types (opentelemetry-sdk)	41s
external-types (opentelemetry-zipkin)	1m 4s
cargo-shear	4m 11s
test (stable, windows-latest)	9m 2s
external-types (opentelemetry)	34s
test (stable, macos-latest)	5m 12s
test (ubuntu-latest, stable)	4m 21s
test (ubuntu-latest, beta)	4m 27s
	59m 1s

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