Remove unused (and broken) functionality in SpanReader #23687

1. 
   sipa commented at 8:49 PM on December 6, 2021: member

   This removes the ability to set an offset in the SpanReader::SpanReader constructor, as the current code is broken since #23653. All call sites use pos=0, so it is actually unused. If future call sites need it, SpanReader{a, b, c, d} is equivalent to SpanReader{a, b, c.subspan(d)}.

   It also removes the ability to deserialize from SpanReader directly from the constructor. This too is unused, and can be more idiomatically simulated using (SpanReader{a, b, c} >> x >> y >> z) instead of SpanReader{a, b, c, x, y, z}.

   This was pointed out by achow101 in #23653 (review).

2. Remove unused (and broken) functionality in SpanReader

   This removes the ability to set an offset in the SpanReader constructor,
   as the current code is broken. All call sites use pos=0, so it is actually
   unused. If future call sites need it, SpanReader{a, b, c, d} is equivalent
   to SpanReader{a, b, c.subspan(d)}.
   
   It also removes the ability to deserialize from SpanReader directly from
   the constructor. This too is unused, and can be more idiomatically
   simulated using (SpanReader{a, b, c} >> x >> y >> z) instead of
   SpanReader{a, b, c, x, y, z}.

   31ba1af74a
3. sipa force-pushed on Dec 6, 2021
4. DrahtBot added the label Wallet on Dec 6, 2021
5. jb55 approved
6. 
   jb55 commented at 12:20 AM on December 7, 2021: member

   crACK 31ba1af74a0aaec690a01ea061264a6d5039d885

   <!-- review by re -->

7. fanquake requested review from MarcoFalke on Dec 7, 2021
8. fanquake requested review from achow101 on Dec 7, 2021
9. 
   achow101 commented at 4:42 AM on December 7, 2021: member

   ACK 31ba1af74a0aaec690a01ea061264a6d5039d885

10. MarcoFalke merged this on Dec 7, 2021
11. MarcoFalke closed this on Dec 7, 2021

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12. 
    shaavan commented at 12:26 PM on December 7, 2021: contributor

    Post merge ACK 31ba1af74a0aaec690a01ea061264a6d5039d885

13. sidhujag referenced this in commit 82cf06c9e2 on Dec 7, 2021
14. 
    jonatack commented at 5:48 PM on December 7, 2021: member

    Posthumous utACK 31ba1af74a0aaec690a01ea061264a6d5039d885

15. RandyMcMillan referenced this in commit 3aa0c2ac7b on Dec 23, 2021
16. DrahtBot locked this on Dec 7, 2022

Review Requested
MarcoFalke