tools: flash2; add a script to use flash2 as reads merger

link to #3911
3 jobs for feature-s/3911-fusion-de-reads-avec-flash in 8 minutes and 31 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test Tools
passed #323180
test_tools

00:00:06

 
  Test Unit
passed #323181
web
test_server_unit

00:00:32

 
  Test Functional
passed #323182
docker x86_64
test_server_functional

00:07:53