PR: Allow user to configure tab close button position

[athompson673]

Description of Changes

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

• Included a screenshot or animation (if affecting the UI, see Licecap)

Desire for user choice to position close buttons on QTabBar's has been expressed in both directions. More complicated tab size calculation mentioned in the linked issue was not attempted due to complexity (compare to tab re-sizing on firefox for example).

Issue(s) Resolved

Fixes #26148

Affirmation

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and understand I am releasing the same under Spyder's MIT (Expat) license.

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[athompson673]

Anyone have thoughts on what is causing the "Linux tests with PyQt6 / Linux - Py3.13, pyqt6, pip, fast/slow" to fail with TypeError: invalid result from CloseButtonTabBarStyle.styleHint(), 'ButtonPosition' object cannot be interpreted as an integer over and over? It's fine on all other testing configurations, and forcing the enum to an int seems to break things as enum.value is not always available.

Edit: fixed

[athompson673]

@ccordoba12 I think the failing test at: spyder/plugins/ipythonconsole/tests/test_ipythonconsole:test_kernel_restart_after_manual_restart_and_crash should not be related to this modification? It's a new error I didn't see in earlier CI runs.