DEV: Add tool to reset js/parse_tests data (#3874)

# Issue

Add tool to reset js/parse_tests data gets out of date easily. Manually
updating it sucks.

# Resolution

Publish a script that copies the "actual" data to the "want" data. DO
NOT CHECK IN THE RESULTS WITHOUT CAREFUL REVIEW.

Author: tlimoncelli

bin/fix_js_parse_tests.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# fix_js_parse_tests.sh -- Fix up the pkg/js/parse_tests "want" files.
+#
+# DO NOT use this without carefully checking the output. You could
+# accidentally codify bad test data and commit it to the repo.
+#
+# Useful bash/zsh alias:
+# alias fixjsparse='"$(git rev-parse --show-toplevel)/bin/fix_js_parse_tests.sh"'
+
+set -e
+
+cd $(git rev-parse --show-toplevel)
+cd pkg/js
+find . -type f -name \*.ACTUAL -print -delete
+go test -count=1 ./... || true
+cd parse_tests
+fmtjson *.json *.json.ACTUAL
+for i in *.ACTUAL ; do f=$(basename $i .ACTUAL) ; mv $i $f ; done