1) Update the LineBreakConfig class to be immutable.
2) Do not return null in the PrecomputedText.Params#getLineBreaiConfig API
Bug: 216638444
Test: atest TextViewTest; atest MeasuredTextTest; atest PrecomputedTextTest; atest TextViewPrecomputedTextTest; atest StaticLayoutLineBreakingVariantsTest
Change-Id: I07766137ff6639c7d4acaad07dbcf11a2841cdb0