13451: ALT key behavior with regard to main menu

[krasko78]

Resolves: #13451 - first part only (second one about the underlined letters needs a discussion)
Should resolve #19239 too although I am going to make an additional change for it (will leave a comment there in a minute)

A pretty simple and straight-forward fix. Works on Windows for me and since the user who has reported #13451 has stated Linux as their OS, I am not limiting this fix to any OS (for now).

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[krasko78]

Regarding the underlined letters: there is an open issue #15134 to not display the underlined letters in the menus if they are open with the mouse, so more opinions are needed here to decide which route we want to go: all always underlined or all underlined only when navigating with the Alt key. Personally I prefer to always see the underlined letters because when I want to open a menu with the keyboard, I look up the underlined letter first and then press ALT + that letter in a single quick gesture. I do not like having to first press ALT, then look up the underlined letter and press it as this feels slow and clumsy. Even if it is one of the modern trends - "modern" does not always mean better...

[zacjansheski]

Tested on MacOS 14, Windows 11, Ubuntu 22.04.3. Approved
#13451 FIXED

Let's move discussion of underlined letters to #15134