Merge remote-tracking branch 'MBradbury/master'
Fix 34571

Switched to UTF8.GetString from using the ASCII encoding. Also, stopped
skipping a test that was dependent on another fix for empty zips.
Merge branch 'master' of https://github.com/IronLanguages/main
Merge pull request #165 from slide/master

Fix 34571
Spelling fixes
Have PythonDictionary and Set implement read only interfaces
Add readonly and sealed where applicable
Change the object used for locking in HybridMapping
Have WithStatement take the header index as a parameter
Remove unused internal variable
Code simplification