Factor out internal flash cache logic

[tannewt]

In #8952 (comment) it was pointed out that this code looked funny:

circuitpython/ports/espressif/supervisor/internal_flash.c

Lines 154 to 157 in 499cc01

	if (_cache_lba != block_address) {
	supervisor_flash_read_blocks(_cache, sector_offset / FILESYSTEM_BLOCK_SIZE, blocks_per_sector);
	_cache_lba = sector_offset;
	}

Specifically the value _cache_lba is set to sector_offset doesn't match the comparison value block_address. This likely causes excess sector reads when writing to the file system. I think the data written is still write. The cache just doesn't work right.

[tannewt]

We should factor out the code that stores an erase sized block and overwrites the writable blocks within it. We have it shared for CP managed external flash but it isn't used for SDK or XIP managed external flash. We should share one implementation based on the external flash implementation because it is most flexible (allocating multiple write sized blocks instead of an erase sized block.) https://github.com/adafruit/circuitpython/blob/main/supervisor/shared/external_flash/external_flash.c#L57