Update Rust toolchain to nightly-2021-09-20 and std to 1.56.1#53

Merged

mssun merged 2 commits intoapache:masterfrom rwwwwww21:update_rust-1.56.1

Nov 23, 2021

+597-590

Commits on Nov 19, 2021

update rust std to 1.56.1
RMheng
committed

Commits on Nov 23, 2021

Use upstream submodules and correct some issues
mssun
committed