Formally define these types and document their meaning.
We will auto-generate the dlv-dap documentation from these Go type doc.
mapToStruct is a helper that sets the given struct's fields with the
info in map[string]interface{} (launch/attach's Arguments). We achieve
this by reencoding map[string]interface{} to json and decoding back to
the target struct. If go-dap left the implementation-specific arguments
as json.RawMessage and let the implementation decode as needed, this
reencoding could've been avoided.
encoding/json itself does not have mean to enforce required fields.
There was a test case that checks substitutePath elements must set
both from/to fields. Path.UnmarshalJSON implements the check.
I am not yet sure about the need for distinction between missing
'from/to' and empty strings yet. (empty value is useful when dealing with
a binary built with trimpath, right?)
A minor behavior change - previously, if noDebug is not a boolean type,
we ignored the attribute silently. Since we use json decoding, any
mismatched types will cause an error and this non-boolean type noDebug
attribute will result in launch failure.
