[Integration][Archery] Add support for setting JS directory by environment variable

[kou]

Describe the enhancement requested

The current implementation assumes that the JS implementation exists in ${ARROW_BUILD_ROOT}/js/:

arrow/dev/archery/archery/integration/tester_js.py

Lines 25 to 29 in 35f8fbc

	ARROW_BUILD_ROOT = os.environ.get(
	'ARROW_BUILD_ROOT',
	Path(__file__).resolve().parents[4]
	)
	ARROW_JS_ROOT = os.path.join(ARROW_BUILD_ROOT, 'js')

${ARROW_BUILD_ROOT} is used by other implementations too. So it's difficult to put the JS implementation to separated directory.

If we can set the JS implementation directory by an environment variable only for this purpose such as ARROW_JS_ROOT, we don't need to copy the JS implementation to ${ARROW_BUILD_ROOT}/js/.

Component(s)

Integration, Archery

[kou]

Issue resolved by pull request 46975
#46975