Bump Qt version to 5.15.2 for Windows builds

[thsfs]

Bumps the Qt version to 5.15.2 for Windows builds. This change makes the builds compatible with the recent compiler related upgrades for C++20.

[thsfs]

There are still some warnings/errors to be sorted out:

2023-05-31T22:08:46.0320580Z qtmain.lib(qtmain_win.obj) : warning LNK4099: PDB '' was not found with 'qtmain.lib(qtmain_win.obj)' or at ''; linking object as if no debug info [D:\a\nano-node\nano-node\build\nano_wallet.vcxproj]
2023-05-31T22:08:46.0322226Z      Creating library D:/a/nano-node/nano-node/build/RelWithDebInfo/nano_wallet.lib and object D:/a/nano-node/nano-node/build/RelWithDebInfo/nano_wallet.exp
2023-05-31T22:08:57.5193797Z   nano_wallet.vcxproj -> D:\a\nano-node\nano-node\build\RelWithDebInfo\nano_wallet.exe
2023-05-31T22:08:57.6182497Z   Building Custom Rule D:/a/nano-node/nano-node/CMakeLists.txt
2023-05-31T22:08:57.8724624Z   -- Install configuration: "RelWithDebInfo"
2023-05-31T22:08:57.8725646Z   -- Installing: C:/Program Files/nano-node/./config-node.toml.sample
2023-05-31T22:08:57.8770223Z   -- Installing: C:/Program Files/nano-node/./config-rpc.toml.sample
2023-05-31T22:08:57.8786402Z   -- Installing: C:/Program Files/nano-node/./nano_wallet.exe
2023-05-31T22:08:57.9371211Z   -- Installing: C:/Program Files/nano-node/./nano_wallet.com
2023-05-31T22:08:58.0057344Z   -- Installing: C:/Program Files/nano-node/./vc_redist.x64.exe
2023-05-31T22:09:01.2483934Z   -- Installing: C:/Program Files/nano-node/./libGLESv2.dll
2023-05-31T22:09:01.5015803Z   -- Installing: C:/Program Files/nano-node/./Qt5Core.dll
2023-05-31T22:09:01.9540960Z   -- Installing: C:/Program Files/nano-node/./Qt5Gui.dll
2023-05-31T22:09:02.4595611Z   -- Installing: C:/Program Files/nano-node/./Qt5Widgets.dll
2023-05-31T22:09:02.8479047Z   -- Installing: C:/Program Files/nano-node/./Qt5WinExtras.dll
2023-05-31T22:09:02.8663403Z   -- Installing: C:/Program Files/nano-node/platforms/qwindows.dll
2023-05-31T22:09:02.9829183Z   -- Installing: C:/Program Files/nano-node/./api/flatbuffers
2023-05-31T22:09:02.9835863Z   -- Installing: C:/Program Files/nano-node/./api/flatbuffers/nanoapi.fbs
2023-05-31T22:09:02.9947460Z   -- Installing: C:/Program Files/nano-node/./nano_node.exe
2023-05-31T22:09:03.0883938Z   -- Installing: C:/Program Files/nano-node/./nano_rpc.exe
2023-05-31T22:09:03.3918053Z "Packaging NSIS"
2023-05-31T22:09:03.3939127Z '"\cpack.exe"' is not recognized as an internal or external command,
2023-05-31T22:09:03.3939917Z operable program or batch file.
2023-05-31T22:09:03.3940271Z "Packaging ZIP"
2023-05-31T22:09:03.3950447Z '"\cpack.exe"' is not recognized as an internal or external command,
2023-05-31T22:09:03.3950883Z operable program or batch file.
2023-05-31T22:09:04.8866646Z SignTool Error: Missing filename.
2023-05-31T22:09:04.9223608Z 
2023-05-31T22:09:05.2014733Z ##[error]Process completed with exit code 1.
2023-05-31T22:09:05.3199856Z Post job cleanup.