RFR: 8371967: Add Visual Studio 2026 to build toolchain for Windows

[Yasumasa Suenaga]

Microsoft has been published Visual Studio 2026, and it can build OpenJDK for Windows without any code changes if we add it to build toolchain.

Now we should support new Visual Studio for maintainability.

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Commit messages:
 - 8371967: Add Visual Studio 2026 to build toolchain for Windows

Changes: https://git.openjdk.org/jdk/pull/28342/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28342&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371967
  Stats: 18 lines in 3 files changed: 15 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/28342.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28342/head:pull/28342

PR: https://git.openjdk.org/jdk/pull/28342