Split tests and fix actual/expected order

test/built-ins/RegExp/lookBehind/alternations.js

...uilt-ins/RegExp/lookBehind/back-references-to-captures.js

test/built-ins/RegExp/lookBehind/back-references.js

test/built-ins/RegExp/lookBehind/captures-negative.js

test/built-ins/RegExp/lookBehind/captures.js

test/built-ins/RegExp/lookBehind/do-not-backtrack.js

test/built-ins/RegExp/lookBehind/greedy-loop.js

test/built-ins/RegExp/lookBehind/misc.js

test/built-ins/RegExp/lookBehind/mutual-recursive.js

test/built-ins/RegExp/lookBehind/negative.js

test/built-ins/RegExp/lookBehind/nested-lookaround.js

test/built-ins/RegExp/lookBehind/simple-fixed-length.js

test/built-ins/RegExp/lookBehind/sliced-strings.js

test/built-ins/RegExp/lookBehind/start-of-line.js

test/built-ins/RegExp/lookBehind/sticky.js

test/built-ins/RegExp/lookBehind/variable-length.js

test/built-ins/RegExp/lookBehind/word-boundary.js

test/built-ins/RegExp/lookbehind.js

test/built-ins/RegExp/negative-lookbehind.js