Partial fix for plot title not updating when plot is open

[jhaigh0]

Description of work

I think this was introduced with some combination of #36393 and mpl updating. If you never set up the call back on the title then it works, but I also had to alter the function to update the axes title (called after changing the plot title in the plot list) which isn't affected by the call back at all.

This PR introduces a couple of draw_idle() calls to try and keep the title rendering up to date. It also adds an override of set_title in the MantidAxes class so that it copies the current font properties to the new text.

The fix is partial because while the text updates, the font properties are not updated until the title is set again (you can even just double-click the title and click okay).

Summary of work

Some (potential useful) other things I found / tried

• Removing the call to get_window_title() and just hard-coding the title as "ws-1" solve the problem, strangely. I tried putting the qt function calls in get_window_title and set_window_title on their own thread using QAppThreadCall but that didn't produce any different results. This makes me think there is some underlying thread issue, possibly also responsible for plotSpectrum() hang #36727.
• Looking at the mpl code for Axes.set_title, two calls to update() are made, first setting the text and default font properties, second setting any specified font properties (i.e fontsize). update() is the function which calls ends up calling the callbacks. I thought if I could notice font property changes in my call back as well as text changes, then I could force a draw_idle for those too. I could never quite get this to work; it began more and more to feel like something I shouldn't be having to do. The two separate calls would point quite nicely to why this fix is only a partial one, with the text updating but not the font properties.

Fixes #36771

To test:

• Run the script from the issue. The title will update text-wise, but not the font size.
• Setting the title through double-clicking the title, changing in the plot settings, changing the title in the plot selector widget (lower left), should then update the title with the new name and correct font size.
• Try running `plt.title("hello123") in the ipython shell, this should update the title too.
• Tests from the PR Add tracking between axis title, window title, and plot name #36393 should all still work

This does not require release notes because it was introduced during 6.9 development.

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[MohamedAlmaki]

Looks good, works as expected. I guess it is better to remove fixes as this PR doesn't fully resolve the issue

[SilkeSchomann]

I think this should go into release-next.

The base branch was changed.