Package visibility improvement for the InputMethodManager

A few APIs in the InputMethodManager disclose the installed input
method packages to apps without holding the query package permission.
This CL filters the caller's access to input methods by rules of
package visibility, except for the currently selected input method.

Updated APIs:
  - getInputMethodList
  - getEnabledInputMethodList
  - getEnabledInputMethodSubtypeList
  - getShortcutInputMethodsAndSubtypes

Bug: 179783492
Bug: 179783499
Bug: 216823971
Test: atest CtsInputMethodServiceHostTestCases
Test: atest CtsInputMethodTestCases
Test: atest CtsInputMethodTestCases32
Test: atest CtsAppEnumerationTestCases
Change-Id: I698b54192b827abeba475df90e099aefe6dd0e18