Add surrounding text to EditorInfo to speed up IME startup

Previously when IMEs want to get initial input text for advanced
prediction featues, it will take up to three IPC calls. Once we provide
the initial text in the EditorInfo object, it would be available right
after the input connection setup and no IPC overheads will be
introduced.

Bug: 122691437
Test: atest FrameworksCoreTests:TextViewTest
Test: atest FrameworksCoreTests:EditorInfoTest
Test: atest CtsWidgetTestCases:TextViewTest
Test: atest CtsInputMethodTestCases:EditorInfoTest
Change-Id: Ie04f2349b1157408aa8ed9044aea12ce99132cb4