[Core] Allow usage of AVRs minimal printf library

[KarlK90]

Description

Introduce new AVR specific make variable AVR_USE_MINIMAL_PRINTF which includes AVR's libc minimal printf implementation. It has less features and thus can shave ~400 bytes.

Usually we use the xprintf implementation but keyboards that use s(n)printf automatically pull in the normal AVR libc implementation, which is ~900 bytes heavy.

Size impact: -390 Bytes

./util/size_regression.sh -d feature/avr_minimal_printf crkbd/rev1:default
Size:    26564, delta:   -390 -- 03900d6e53 Enable for crkbd (not actually in PR)
Size:    26954, delta:     +0 -- 3eb1f765a1 [Core] Allow usage of AVR minimal printf library

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[stale]

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