security/meek: Update 0.21 -> 0.31

Port changes:

• Switch to the original torproject.org upstream
• Remove dependency on packaged Go libs
• Add LICENSE and LICENSE_FILE

PR: 230013
Submitted by: Dmitri Goutnik <dg@syrec.org>
Approved by: cs (maintainer's timeout; 36 days)
Differential Revision: D16411