CLI: Fix crash with unexpected plugin files

[WillyJL]

What's new

• simply ignores unexpected files in CLI plugins dir instead of crashing
• this is because some CFWs had their own CLI plugin system before with a different naming scheme, and some of those leftover plugin files caused people moving from CFW to OFW to crash when connecting to qFlipper / lab.flipper.net (sorry about that 😅)

Verification

• put any file in /ext/apps_data/cli/plugins/ that does not start with cli_ or does not end with .fal
• flipper should ignore it when plugging into qFlipper / lab.flipper.net instead of crashing

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix