adding freertr to the suite

[mc36]

if you're interested in a java based, heavily multi-threaded implementation then here we go... :) for now, it statically sets the java heap to 4gb, for (multiple) full tables, that could be low....

after running "bgperf2.py bench -t freertr" i got:

freertr,freertr,25.9.17,100,100,9900,10000,6,4,2,2,25.63,348,0.748,100,6.067,,2025-09-17,4,7.76GB,0,0,,,