[REVERT?] xt: add eml ->as_string round trip checker

[Eric Wong <e@80x24.org>]

Eric Wong <e@80x24.org> wrote:
> Unlike Email::MIME, PublicInbox::Eml::as_string should be able
> to round trip from the Perl object to a raw scalar and back
> without changes.

Well, almost...  As long as we don't use ->each_part.
Will likely go with this revert:

----------8<----------
Subject: [PATCH] xt: remove eml_check_roundtrip

If there's no body ({bdy} field), ->each_part set the {bdy}
field to "\n" and the ->as_string result afterwards is one
extra "\n" byte longer than the original.

It's not worth extra cycles in common ->each_part calls to
ensure 100% round-trip matches of header-only messages (which
are likely spam), especially when the only difference is a
trailing "\n".
---
 MANIFEST                 |  1 -
 xt/eml_check_roundtrip.t | 43 ----------------------------------------
 2 files changed, 44 deletions(-)
 delete mode 100644 xt/eml_check_roundtrip.t

diff --git a/MANIFEST b/MANIFEST
index 65fa8736..b6a681e9 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -385,7 +385,6 @@ t/xcpdb-reshard.t
 xt/cmp-msgstr.t
 xt/cmp-msgview.t
 xt/eml_check_limits.t
-xt/eml_check_roundtrip.t
 xt/git-http-backend.t
 xt/git_async_cmp.t
 xt/httpd-async-stream.t
diff --git a/xt/eml_check_roundtrip.t b/xt/eml_check_roundtrip.t
deleted file mode 100644
index 9b216c53..00000000
-- 
--irreversible-delete was used with git-format-patch