test: generate utf-16 testdata and bom variants

gen_testdata.go

main_test.go

testdata/utf-16be/data-error.json

testdata/utf-16be/data-error.yml

testdata/utf-16be/data-fail.json

testdata/utf-16be/data-fail.yml

testdata/utf-16be/data-pass.json

testdata/utf-16be/data-pass.yml

testdata/utf-16be/schema.json

testdata/utf-16be/schema.yml

testdata/utf-16be_bom/data-error.json

testdata/utf-16be_bom/data-error.yml

testdata/utf-16be_bom/data-fail.json

testdata/utf-16be_bom/data-fail.yml

testdata/utf-16be_bom/data-pass.json

testdata/utf-16be_bom/data-pass.yml

testdata/utf-16be_bom/schema.json

testdata/utf-16be_bom/schema.yml

testdata/utf-16le/data-error.json

testdata/utf-16le/data-error.yml