`Intl.NumberFormat.prototype.format` should allow both with/without spaces around numbers

[Gumichocopengin8]

For the Intl.NumberFormat test cases with ja-JP and zh-TW locales, it has been observed that spaces appear before and after the number when using long for unitDisplay.

test262/test/intl402/NumberFormat/prototype/format/unit-ja-JP.js

Line 58 in f0dc15c

"long": "時速 987 キロメートル",

However, these spaces are not explicitly specified in the ECMA-402 specification.

const nf = new Intl.NumberFormat("ja-JP", { style: "unit", unit: "kilometer-per-hour", unitDisplay: 'long' });
nf.format(987)

Given this observation, both of the following formats should be considered acceptable outputs for the above code:

• 時速 987 キロメートル
• 時速987キロメートル
  and even these too?
• 時速 987キロメートル
• 時速987 キロメートル