Merge upstream 0.3.0 beta into our fork for less unsafe#21

mrhrzg wants to merge 8 commits intomastersignavio/antlr4rust:masterfrom

merge_upstream_0.3.0-beta_into_our_forksignavio/antlr4rust:merge_upstream_0.3.0-beta_into_our_forkCopy head branch name to clipboard