Add designated runner for perf jobs.

[rectified95]

Description

Adding dedicated runner for the km_performance job.

Note on labels: in reusable-test.yml the condition to check for self-hosted runners uses both the ebpf_cicd_tests and ebpf_cicd_perf labels, while every self-hosted runner gets the self-hosted label by default. However, the self-hosted label is useful/needed for runner migrations, so I chose not to use it; also we shouldn't have more than 2/3 different runner types (likely +1 for stress tests), so these expressions won't grow indefinitely.

Also, setting the job to only run in Release configuration. Since the tests don't work in Debug, we can halve the time the designated runner is occupied.

Testing

Successful run of the bpf_performance job forced to execute on commit push. Restoring original behavior of event-triggered runs.
[10:10:15] :: Timestamp,Test,Average Duration (ns),CPU 0 Duration (ns)
[10:10:15] :: 2023-09-13T17:10:15-0800,Baseline,17,17
[10:10:16] :: 2023-09-13T17:10:15-0800,bpf_get_prandom_u32,25,25
[10:10:16] :: 2023-09-13T17:10:16-0800,BPF_MAP_TYPE_ARRAY read,48,48
[10:10:17] :: 2023-09-13T17:10:16-0800,BPF_MAP_TYPE_ARRAY update,45,45
[...]
https://github.com/microsoft/ebpf-for-windows/actions/runs/6175281298/job/16762541899?pr=2845

Documentation

Will follow up with a more thorough update to the setup guide.

[codecov]

Codecov Report

Merging #2845 (e86101a) into main (01bc766) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2845   +/-   ##
=======================================
  Coverage   86.68%   86.69%           
=======================================
  Files         141      141           
  Lines       26182    26182           
=======================================
+ Hits        22697    22698    +1     
+ Misses       3485     3484    -1     

see 2 files with indirect coverage changes