Reduce buffer size when writing partial ids

[RobinTF]

This PR reduces the arbitrary buffer size of 1GB used to buffer IO writes for ids when parsing with an equally arbitrary 8MB buffer, which shows no difference in performance in small scale testing, but reduces the memory footprint by almost a whole GB.

[sparql-conformance]

Overview

Number of Tests	Passed ✅	Intended ✅	Failed ❌	Not tested
548	447	73	28	0

Conformance check passed ✅

No test result changes.

Details: https://qlever.dev/sparql-conformance-ui?cur=a6e59f886d75f0250103d6807383c7dc8afdaff8&prev=f54b0a34f8d91af3bbdb7dbc32f115d295e11c31

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.38%. Comparing base (04f32a1) to head (a6e59f8).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2857   +/-   ##
=======================================
  Coverage   92.37%   92.38%           
=======================================
  Files         510      510           
  Lines       44109    44118    +9     
  Branches     5834     5833    -1     
=======================================
+ Hits        40746    40758   +12     
+ Misses       1702     1701    -1     
+ Partials     1661     1659    -2     

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