This fixes some consistency problems with how number strings were parsed
in the msgpack decoder vs other situations.
This commit also includes an upgrade of HCL2 to use this new cty function,
though there's no change in behavior here since the new function is
functionally equivalent to what it replaced.
This is largely minor bugfixes for issues found since we last updated the
vendoring. There are some new features here that Terraform is not yet
using and thus present little risk.
In particular this includes the HCL-JSON spec change where arrays can now
be used at any level in a block label structure, to allow for preserving
the relative order of blocks.