fix(benchmark): write benchmark results to file

[pichlermarc]

Which problem is this PR solving?

Benchmark workflow is currently failing because individual benchmark results are not written to file. This PR makes it so that benchmark results are written to .benchmark-results.txt and adds .benchmark-results.txt to .gitignore.

Related #4171

Type of change

• Bug fix (non-breaking change which fixes an issue)

[codecov]

Codecov Report

Merging #4172 (0bffc31) into main (c84698d) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head 0bffc31 differs from pull request most recent head 5c9a206. Consider uploading reports for the commit 5c9a206 to get more accurate results

@@            Coverage Diff             @@
##             main    #4172      +/-   ##
==========================================
+ Coverage   92.24%   92.25%   +0.01%     
==========================================
  Files         331      331              
  Lines        9465     9465              
  Branches     1997     1997              
==========================================
+ Hits         8731     8732       +1     
+ Misses        734      733       -1     

see 1 file with indirect coverage changes

[martinkuba]

Thank you for catching this!