RFR: 8323801: <s> tag doesn't strikethrough the text

[Alexey Ivanov]

When `<s>` tag is used inside `<u>`, the `line-through` style is lost, and the text is rendered with `underline` only. However, if `<strike>` is used, the text is rendered with both `underline` and `line-through` styles.

Both `<s>` and `<strike>` should render the text the same way.

-------------

Commit messages:
 - 8323801: Test case for <s> vs <strike>
 - 8323801: Handle <s> as <strike>

Changes: https://git.openjdk.org/jdk/pull/17659/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17659&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323801
  Stats: 127 lines in 2 files changed: 117 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/17659.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17659/head:pull/17659

PR: https://git.openjdk.org/jdk/pull/17659