LIST-EXTENDED, part 1: response data item types

[soywod]

The LIST-EXTENDED is a big piece, so I decided to split into independent PRs. Here the part 1 that contains the response data item types.

Refs: #350

[coveralls]

Coverage Report for CI Build 30464725878

Coverage decreased (-0.1%) to 91.249%

Details

• Coverage decreased (-0.1%) from the base build.
• Patch coverage: 17 uncovered changes across 2 files (34 of 51 lines covered, 66.67%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
imap-types/src/extensions/list_extended.rs	48	34	70.83%
imap-types/src/arbitrary.rs	3	0	0.0%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	11645
Covered Lines:	10626
Line Coverage:	91.25%
Coverage Strength:	913.21 hits per line

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💛 - Coveralls

[soywod]

Coverage should improve by itself with codec-related changes (future PRs).

[duesee]

Looks good to me!

I would still need more time to read the RFC and validate all the details to vouch for it. But this is unfortunately not possible for me time-wise currently.

What do you think about this approach? We feature-gate the extension (which is our "still experimental marker") and then we can be generally more relaxed about the code, interface, structure, .... I would then basically do my best to guide you but otherwise just trust that you got the details right. If you notice (in production) that something still needs to change, we can just do the change w/o worrying about semver too much.