Support `ErrorRef` in `#` error formatter #63

Job	Run time
test (stable minus 15 releases)	1m 27s
test (stable minus 15 releases, nested-values)	1m 31s
test (stable minus 15 releases, dynamic-keys)	1m 24s
test (stable minus 15 releases, nothreads)	1m 23s
test (stable minus 15 releases, nested-values dynamic-keys)	1m 35s
test (stable minus 15 releases, nested-values dynamic-keys nothreads)	1m 29s
test (1.56)	1m 29s
test (1.56, nested-values)	1m 31s
test (1.56, dynamic-keys)	1m 23s
test (1.56, nothreads)	1m 24s
test (1.56, nested-values dynamic-keys)	1m 34s
test (1.56, nested-values dynamic-keys nothreads)	1m 33s
test (1.72)	13s
test (1.72, nested-values)	23s
test (1.72, dynamic-keys)	15s
test (1.72, nothreads)	15s
test (1.72, nested-values dynamic-keys)	22s
test (1.72, nested-values dynamic-keys nothreads)	23s
test (stable)	16s
test (stable, nested-values)	20s
test (stable, dynamic-keys)	12s
test (stable, nothreads)	12s
test (stable, nested-values dynamic-keys)	18s
test (stable, nested-values dynamic-keys nothreads)	21s
test (nightly)	12s
test (nightly, nested-values)	17s
test (nightly, dynamic-keys)	15s
test (nightly, nothreads)	12s
test (nightly, nested-values dynamic-keys)	18s
test (nightly, nested-values dynamic-keys nothreads)	21s
test (1.49)	1m 22s
test (1.49, dynamic-keys)	1m 19s
test (1.49, nothreads)	1m 32s
test (1.49, nothreads dynamic-keys)	1m 22s
	28m 23s

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