Add option to hide title bar when not showing menu bar

[DorianRudolph]

This PR fixes #43154 by adding an option to hide the custom title bar when it is not needed to display the menu bar (i.e., for "toggle" and "compact" visibility settings).

The use case is Linux with tiling window manager (sway for me). Sway and other tiling window managers can draw their own title bars as seen below.

The functionality of this PR is similar to #117149, though it is not concerned with zen mode.

[ghost]

All CLA requirements met.

[sbatten]

@DorianRudolph Why would one use the custom titlebar option only to draw a native titlebar?

[DorianRudolph]

Sorry if my explanation regarding tiling window managers was unclear.
Here is how my screen layout looks while working:

The small title/tab bars above the windows belong to the tiling window manager sway. They are unrelated to this PR and can also be disabled:

In the above screenshot you can compare VSCode with the title bar on the right vs. without on the left.

Without the title bar, I can get about 2 extra lines of code on screen, which on a smaller laptop can be significant.

VSCode with the native title bar enabled looks as follows:

But the native title bar has two downsides for me.
First, this displays the menu bar and context menu using GTK (following the OS theme), not directly in VSCode. If find the latter looks nicer and more coherent.
Second, now I don't have the option to hide the menu bar and use the toggle/compact menu bar settings.

[CleoMenezesJr]

Too bad this Merge was blocked. I don't understand why the problem of giving options to the user when it is deliberately possible.

[Titaniumtown]

Yea. sucks, this would be a very good feature :(

[robsontenorio]

Maybe some plugin can solve it?