[1.0] Use BetterNodeFinder::resolveNextNode() on DowngradeNegativeStringOffsetToStrlenRector

[samsonasik]

@TomasVotruba @staabm this require PR on rector-src:

• [1.0] Add public method BetterNodeFinder::resolvePreviousNode() and BetterNodeFinder::resolveNextNode() rector-src#3896

this cover next node of: String_, Variable, PropertyFetch, StaticPropertyFetch.

for adding BetterNodeFinder::resolvePreviousNode() and BetterNodeFinder::resolveNextNode() to be merged first.

[samsonasik]

@TomasVotruba it works 🎉 , PR in rector-src need to be merged first for it:

• [1.0] Add public method BetterNodeFinder::resolvePreviousNode() and BetterNodeFinder::resolveNextNode() rector-src#3896

then normal rector-src dev-main without pin hash can be rolled back.