refactor: modernize deprecated ipc headers #32781

1. 
   Sjors commented at 2:31 pm on June 19, 2025: member

   Split off from #31802.

   Pre-empt tidy warning when multiprocess is on by default:

   0[10:33:51.654] /ci_container_base/src/ipc/capnp/protocol.cpp:20:10: error: inclusion of deprecated C++ header 'errno.h'; consider using 'cerrno' instead [modernize-deprecated-headers,-warnings-as-errors]
   1[10:33:51.654]    20 | #include <errno.h>
   2[10:33:51.654]       |          ^~~~~~~~~
   3[10:33:51.654]       |          <cerrno>
   4[10:33:51.654] 919 warnings generated.
   

   https://github.com/bitcoin/bitcoin/pull/31802/checks?check_run_id=43968493627

2. refactor: modernize deprecated ipc headers

   Co-authored-by: fanquake <fanquake@gmail.com>

   74b7e9c7db
3. DrahtBot added the label Refactoring on Jun 19, 2025
4. 
   DrahtBot commented at 2:31 pm on June 19, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32781.

   Reviews

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   Type	Reviewers
   ACK	maflcko, ryanofsky
   Concept ACK	enirox001

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5. 
   maflcko commented at 2:38 pm on June 19, 2025: member

   lgtm ACK 74b7e9c7dbf73b6df84ba8a1f40dd22924a604ef
6. 
   enirox001 commented at 9:05 am on June 20, 2025: contributor

   Looks good to me

   ACK

7. ryanofsky approved
8. 
   ryanofsky commented at 3:32 pm on June 20, 2025: contributor

   Code review ACK 74b7e9c7dbf73b6df84ba8a1f40dd22924a604ef
9. fanquake merged this on Jun 23, 2025
10. fanquake closed this on Jun 23, 2025

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Contributors
Sjors DrahtBot maflcko enirox001 ryanofsky

Labels
Refactoring