[Settings] enhancing data saver config control

Enhancing the control of R.bool.config_show_data_saver when false, which including:
1. Initial presentation is invisible
2. Leaving UI when triggered
3. Avoid from getting searched
4. Robolectric test case support

Bug: 243877672
Test: test cases and local testing
Merged-In: I909522c0244ebb012a27d6aff34120a4f90128c6
Change-Id: I909522c0244ebb012a27d6aff34120a4f90128c6