reduce default number of routing in-process requests

[gammazero]

Reduce the routing ProviderQueryManager default MaxInProcessRequests from 16 to 8. This prevents a situation where goroutines can be created faster than they can be completed, leading to OOM.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.47%. Comparing base (8ca0ca2) to head (a2d9527).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #793      +/-   ##
==========================================
- Coverage   60.51%   60.47%   -0.04%     
==========================================
  Files         245      245              
  Lines       31132    31130       -2     
==========================================
- Hits        18840    18827      -13     
- Misses      10615    10625      +10     
- Partials     1677     1678       +1     

Files with missing lines	Coverage Δ
bitswap/client/client.go	86.61% <100.00%> (-2.20%)	⬇️
...uting/providerquerymanager/providerquerymanager.go	85.76% <100.00%> (-0.98%)	⬇️

... and 4 files with indirect coverage changes