getVariableDeclaration - Search object and array binding patterns for name

[dsherret]

For example, given the following variable statement:

const { a, b } = { a: 1, b: 2 };

Doing:

const variableDec = sourceFile.getVariableDeclarationOrThrow("a");

Should return the VariableDeclaration with the ObjectBindingPattern. The same should happen when searching for variable statements.

From #519.