Because the health check uses OS specific syscalls for determining the
available space on a disk that aren't available in JS/WASM builds, we
need to make sure we don't reference that code at all. Otherwise we
can't use parts of lnd as a library in projects that are being compiled
down to a WASM binary.
With this commit we rename the existing AvailableDiskSpace function to
its correct name AvailableDiskSpaceRatio as it only returns a ratio. We
then go ahead and add a new function that returns the actual number of
free bytes available on a file system.
This also fixes some comments and always returns an error instead of
panicking.
In this commit, we bump up the logging for failed healthchecks from
`debug` to `info`. This should help us get to the bottom of the current
set of reported false positives that are causing `lnd` nodes to
erroneously shutdown.
Add a new health check package which will periodically poll health
check functions and shutdown if we do not succeed after our set number
of attempts. The first check that we add is one for our chain backend,
to ensure that we are connected to a bitcoin node.
