Code cleanup in src\java.desktop\share\classes\javax\swing\tree\VariableHeightLayoutCache.java

As part of analysis of JDK-8187936, some problems/cleanup tasks have been identified in VariableHeightLayoutCache.java:
1. Line 927: Uninitialized variables, checking for trivial reject case multiple times.
2. Line 999: Traditional code written to find maximum size of components, which can be done without any local variables and explicit looping with streams.
3. Line 1365: Code repetition for differenct conditions, which can be ored together to reduce the repetition.
4. Line 1482: A large code block gets repeated only because of different values need to be passed in one line. This can be moved to a variable initialization, and the repeating code blocks can be reduced to one.
5. Line 1505: Variable initialization can be simplified by combining different conditions.
6. Line 1540: An explicit loop to apply a function over a collection, can be achieved in one line by a forEach construct.
7. Line 1747: Combine all the trivial reject cases into one condition, and also, a potential bug which increments the "nextIndex" value beyond the length of the containing elements. The increment should happen only if the trivial reject case fails.