buildx/bake/hclparser
Justin Chadwell 03885ec9f1 hclparser: strip out blocks for json files
Body.JustAttributes cannot distinguish between blocks and attributes for
JSON files, so the variable block could be included in the list of
attributes returned.

This patch ensures that JSON and HCL files behave the same way by
removing all known block types first, from the provided config schema
and then from a generated definitions schema.

Fixes 

Signed-off-by: Justin Chadwell <me@jedevc.com>
..
expr.go bake: new hclparser package
hclparser.go hclparser: strip out blocks for json files
stdlib.go bake: new hclparser package