Bootloader size optimizations

[hedger]

What's new

• Removed -u _printf_float linker flag for bootloader project - drastically reduces binary size
• Removed Bluetooth-specific init in BL - also removes snprintf dependency, further reducing binary size. Anyway, furi_hal_version.device_name[0] was zeroed-out after all string formatting shenanigans.
• Introduced SLIM_BOOTLOADER definition (NOT active by default) - when defined, removes Update & Recovery Mode from bootloader screen, saving ~3kb on font data. That string can be included in splash screen bitmap, storing it much more efficiently.

Verification

• Build, check basic bootloader functionality and reduced size.

Checklist (do not modify)

• 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