Import upstream v0.16.22, stripped

Upstream commit: 474dd0229cb20cf513036619781ed97bd8073c3f
Enterprise-only files removed or emptied: 63
Enterprise-only snippets removed: 117 in 50 files
Dangling module declarations removed: 5
Cargo edits turning enterprise off: 14
Verification: clean
Enterprise feature gates left for rebuilt features: 19 in 18 files

Produced by tools/fork/strip.py. The full report is in docs/fork/strip-reports/ on main.

tests/resources/imap/003.txt

@@ -0,0 +1,25 @@
+From: Nathaniel Borenstein <[email protected]>
+To: Ned Freed <[email protected]>
+Date: Mon, 22 Mar 1993 09:41:09 -0800 (PST)
+Subject: Formatted text mail
+MIME-Version: 1.0
+Content-Type: multipart/alternative; boundary=boundary42
+
+--boundary42
+Content-Type: text/plain; charset=us-ascii
+
+... plain text version of message goes here ...
+
+--boundary42
+Content-Type: text/enriched
+
+... RFC 1896 text/enriched version of same message
+    goes here ...
+
+--boundary42
+Content-Type: application/x-whatever
+
+... fanciest version of same message goes here ...
+
+--boundary42--
+