fix :leaks contribution fragment

[rovertrack]

follow up for #6705

Fixes #6692

What changes did you make and why?
ContributionController.kt

• Added a cleanup() method to nullify locationPermissionCallback and locationPermissionsHelper

ContributionsFragment.kt

• Calls the cleanup method contributionController?.cleanup() in onDestroyView()
• Added cleanup logic to nullify mediaDetailPagerFragment to prevent leaking it when removed

ContributionsListFragment.k

• Nullifies controller as the leak persisted when tab switching

MainActivity.kt

• In freeUpFragments(), nullifies contributionsFragment which was previously left out causing a leak
• Updated loadFragment to reuse contributionsFragment without leaking it

Screenshots (for UI changes only)

[github-actions]

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