Rename them so they end in txt instead of cfg, then use the exec console command. For example, if you rename it addons.txt, you would run exec addons.txt.
If you wanted to get fancy, you could then create a new autoexec.cfg that contains nothing but alias launchaddons "exec addons.txt". This basically lets you add a custom console command; you would just run launchaddons in the console and your commands in addons.txt would run.
Check the wiki article on console commands for more info.