Add configuration for lenses in lsp-rust.el: (#4103) #4641

Job	Run time
test (ubuntu-latest, 26.3, false)	2m 50s
test (ubuntu-latest, 27.2, false)	3m 13s
test (ubuntu-latest, 28.2, false)	3m 30s
test (macos-latest, 26.3, false)	4m 48s
test (macos-latest, 27.2, false)	7m 25s
test (macos-latest, 28.2, false)	6m 9s
test (windows-latest, 26.3, false)	8m 21s
test (windows-latest, 27.2, false)	3m 42s
test (windows-latest, 28.2, false)	4m 13s
test (ubuntu-latest, snapshot, true)	3m 10s
test (macos-latest, snapshot, true)	5m 37s
test (windows-latest, snapshot, true)	1m 19s
	54m 17s

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