Update to build with recent Rust and benchmark point range queries

[msfroh]

Hi there! A couple of us (myself and @harshavamsi) were looking into Lucene's range query performance and wanted to compare against other implementations, including Rucene and Tantivy.

In order to get Rucene compiling with modern Rust, we had to make a number of changes, mostly around names of things (e.g. get_{ref,mut} became assume_init_{ref,mut} for MaybeUninit), but also we had to fix a bunch of "undefined behavior" errors related to interior mutability.

This PR also contains the range query benchmark harness that we built for our experiment (plus a flamegraph from profiling Rucene on those benchmarks). We can remove those from this PR if needed. I just wanted to make sure to surface the build fixes that we've done in case they help someone else.