klipper: port to SQLite

Reason for the change

This allows saving more formats in the database. In theory, the memory consumption should be lower when there are many images.

The database now depends on SQLite and there are 3 tables in the database.

1. main: stores data used by the frontend
2. aux: stores mime type and data index
3. version: stores the database version, used in the future when the table changes.

• Fix tests
• Use local paths for images
• Limit the data size a clip can store
• Test migration
• vaccum

Test plan

Pass all clipboard tests

Screenshots or screen recordings

Bugs fixed

BUG: 491961 FIXED-IN: 6.3

Closes #67 (closed)

Alternative to !4636 (closed)