The https://github.com/super-linter/super-linter/pull/6113 introduced
new Git merge conflicts linter check, that is error prone in some
conditions (see screenshot).
This PR adjusts this check to be more precise and exact in a way that
all three markers should be found to identify check as failed.
Additionally improve Git merge conflict markers matchers.
Co-authored-by: Marco Ferrari <ferrari.marco@gmail.com>