- Start saving instructions as the whole PR was >1KB long.
- It turned out the compiler was unable to understand the core skipping
cycle and an ASM version had to be used.
- Add seekSet aware of the G-code filter
This is an extension/optimization of PR #2956.
It uses the cached 512B block buffer to avoid heavy-weight read() in SdBaseFile.
Even though this principle allowed the AVR to skip ~600KB of data within ~5 seconds,
the impact on code base is huge, especially into well proven and long-term stable
parts like reading a file from the SD card.
The sole purpose of this PR is to show/verify the possibility of the AVR CPU
in relation to adding thumbnails into MK3 G-codes.
Moreover, this PR shall not be merged unless the missing/commented features
are restored - especially file seeking and M84 search.
PFW-1175
