RFR: 8326948: Force English locale for timeout formatting

[Alexey Ivanov]

If a test runs in non-English locale, the digits displayed in the timeout could be locale-specific, which may be confusing.

For example, in the Arabic locale `-Duser.language=ar`, the timeout is displayed like this:

Test timeout: ٠٠:٠٤:٥٨

The fix explicitly sets English locale for formatting, which ensures the timeout is always displayed with the Western Arabic numerals, see [Numerals in most popular systems](https://en.wikipedia.org/wiki/Numerical_digit#Numerals_in_most_popular_systems).

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Commit messages:
 - 8326948: Force English locale for timeout formatting

Changes: https://git.openjdk.org/jdk/pull/18042/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18042&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326948
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18042.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18042/head:pull/18042

PR: https://git.openjdk.org/jdk/pull/18042