Interrupt query yielding rows.

[MathieuBordere]

Allow to interrupt a query yielding rows, whereas in the past the interrupt request was only handled - after - all rows were returned.

To make this work I had to allow multiple pending writes to the transport because the query that's yielding rows is writing to the transport, but when an interrupt comes in, we also want the interrupt handler to be able to write to the transport. As long as messages are written as whole and uv_write_t doesn't interleave data of 2 writes [1] then this should be okay.

DRAFT: running tests and upstream tests and also want to check if I'm violating some assumptions by allowing multiple writes, basically checking [1].

EDIT: writes with uv_write_t are queued and execute in order, so multiple writes should be fine. dqlite also sends data with message granularity, so that should also be fine.

[MathieuBordere]

please test downstream

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (71562ee) 61.29% compared to head (0976158) 61.31%.

Files	Patch %	Lines
src/conn.c	87.50%	0 Missing and 2 partials ⚠️
src/lib/transport.c	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #560      +/-   ##
==========================================
+ Coverage   61.29%   61.31%   +0.02%     
==========================================
  Files          34       34              
  Lines        6834     6838       +4     
  Branches     2031     2033       +2     
==========================================
+ Hits         4189     4193       +4     
+ Misses       1349     1345       -4     
- Partials     1296     1300       +4     

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[MathieuBordere]

please test downstream

[cole-miller]

Hooray!