review: perf: reduce overhead of isLocalType check

[SirYwell]

Those are two very related performance improvements. While they aren't that significant, it might add up for larger projects.

1. When using TypeFactory#get(String) with a nested type, the method extracts the outer type string, gets that type recursively and uses its reference to check if it is a local type. The implementation of isLocalType then accesses its type again and calls the isLocalType method of the type. We can just skip this indirection by calling isLocalType on the type directly.

2. Previously, the isLocalType implementation of the reference accessed the declaration twice (= building the qualified name and passing it to TypeFactory#get(String) as mentioned in 1.) This is only needed once, so we reuse the returned value.

I also saw that if the declaration in 2. is null, there is a regex pattern

spoon/src/main/java/spoon/support/reflect/reference/CtTypeReferenceImpl.java

Lines 524 to 526 in d9bcb11

	final Pattern pattern = Pattern.compile("^([0-9]+)([a-zA-Z]+)$");
	final Matcher m = pattern.matcher(getSimpleName());
	return m.find();

which isn't efficient in itself. I didn't change that because the implementation is also wrong here, because something like 1LocalType1 would not be matched. I will address that separately.

[slarse]

LGTM, thanks @SirYwell. Hard to gauge how much of a performance improvement this provides, but it's definitely not going to be worse and reads a bit better to boot.