dspinner: RecursiveKeys(): do not hang on cancellations

[hsanjuan]

Per ipfs/kubo#10593, if no one is reading from the channel returned by RecursiveKeys() and the context is cancelled, streamIndex will hang indefinitely.

Proposed fix is to always select when attempting to write to the out channel. If the context is done and there is no one to read, we can abort.

[codecov]

Codecov Report

Attention: Patch coverage is 36.36364% with 7 lines in your changes missing coverage. Please review.

Project coverage is 60.30%. Comparing base (91c4d50) to head (7502f79).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pinning/pinner/dspinner/pin.go	36.36%	6 Missing and 1 partial ⚠️

@@            Coverage Diff             @@
##             main     #727      +/-   ##
==========================================
- Coverage   60.35%   60.30%   -0.06%     
==========================================
  Files         244      244              
  Lines       31029    31034       +5     
==========================================
- Hits        18728    18715      -13     
- Misses      10632    10650      +18     
  Partials     1669     1669              

Files with missing lines	Coverage Δ
pinning/pinner/dspinner/pin.go	58.46% <36.36%> (-0.26%)	⬇️

... and 12 files with indirect coverage changes