[FL-3888] Make file extensions case-insensitive

[gsurkov]

What's new

• Treat file extensions as case-insensitive in Archive and Browser
• Add furi_string_ends_withi() function family for case-insensitive checks
• Fixes File browser extension filters are case-sensitive #3492

Verification

1. Create several supported files with varying extension case, e.g. Remote1.ir, Remote2.IR, etc.
2. Ensure that all of these files are shown with correct icons both in Archive app and when opening files, e.g. from the Infrared app.
3. Ensure that there is no false positives (files with incorrect extensions must not be shown or shown as unknown files depending on the use case).

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

[github-actions]

Compiled f7 firmware for commit 8c4fba1d:

• 📦 Update package
• 📥 DFU file
• ☁️ Web/App updater
• 📊 Size report