The lowest limitation I've seen on any filesystem we care about is 255
characters. 230 leaves enough space that an index or field could be
backed up and have a timestamp and file extension appended while
still allowing for much longer index and field names.
This commit implements BSI with variable bit depth using a
sign magnitudeto indicate whether a value is positive or negative.
This also rearranges the existence bit to be the first bit instead
of the last bit.
So with the switch to a new linter, we get a lot of new warnings,
and the majority of them are harmless probably, but a few might be
real. Variously just use _ to suppress warnings, or report errors.
There's probably things here that deserve better fixes, but we can
always revisit it.
This commit adds the ability to remove an 'available shard'
from the shard cache. This does not affect shards known to be
available because of local data.