Remove potentially problematic memory optimization in BlockSubLevelLiftProvider - #1419

Avoid using "globals to avoid allocation", this way JIT can do proper escape analysis, do proper optimizations (and make the function thread-safe too)

More details on escape analysis:
https://docs.oracle.com/javase/8/docs/technotes/guides/vm/performance-enhancements-7.html#escapeAnalysis

There are many reasons why I would not create globals to avoid allocation:

• Escape analysis can stack promote all the internal vectors (that cannot leave the function scope), stack promoted things can be promoted to registers
• even if allocated, allocations will be in current cache, it is less likely for the code to cache-miss.
• updating object fields would slow-down the function more (since GC barriers are a thing), this way that doesn't happen.
• since I can avoid TEMP, the math is a bit more readable.
• accidentally made the function thread-safe.

I was thinking on what might be worse with this, but I couldn't find many reasons. Some allocations will occur before JIT compiles the function, but that probably doesn't matter (since compilation will happen pretty fast)
Also because this patch removes a few fields, it might break some mods, so merging this might be a bit risky.

And since the function isn't a performance bottleneck anyway, I would say this PR is pretty low priority.