When building with VS2026 on Windows, use PlatformToolSet v145 by default #144679

As discussed offline with @zooba and @Fidget-Spinner as a preparational step to be able to use tailcalling (#139922) for the official Windows binaries beginning with 3.15.

Linked PRs

• GH-144679: When building with VS2026 on Windows, use PlatformToolSet v145 by default #144680
• GH-144679: MSVC tailcall CI no longer needs to specify PlatformToolset #145004
• GH-144679: Upgrade to windows-2025-vs2026 in GitHub Actions #145005
• [3.14] GH-144679: When building with VS 2026 on Windows, use PlatformToolset v145 by default (GH-144680) #158188