fix: vulnerable to cross-app script injection via crafted intent

[farhan-arshad-dev]

Description

LEARNER-9557

• Mitigated the vulnerability by disabling the ability to open custom-defined inner URIs through external sources. This was achieved by setting android:exported="false".
• Setting android:exported="false" for the android component doesn't need to call outside from the app.

Testing

• [ ] App should open a custom-defined URI or URL via browser OR crafted intent through other apps.

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (bcf1d6d) 1.08% compared to head (086b84e) 1.07%. Report is 5 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1833 +/- ## =========================================== - Coverage 1.08% 1.07% -0.01% Complexity 137 137 =========================================== Files 538 538 Lines 26293 26300 +7 Branches 3381 3384 +3 =========================================== Hits 284 284 - Misses 25982 25989 +7 Partials 27 27 ``` [see 4 files with indirect coverage changes](https://app.codecov.io/gh/openedx/edx-app-android/pull/1833/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=openedx)

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