The length passed to IDP_NewString included the nil terminator
unlike IDP_AssignString. Callers to IDP_AssignString from MOD_nodes.cc
passed in an invalid size for e.g. There where also callers passing in
the strlen(..) of the value unnecessarily.
Resolve with the following changes:
- Add `*MaxSize()` versions of IDP_AssignString & IDP_NewString which
take a size argument.
- Remove the size argument from the existing functions as most callers
don't need to clamp the length of the string, avoid calculating &
passing in length values when they're unnecessary.
- When clamping the size is needed, both functions now include the nil
byte in the size since this is the convention for BLI_string and other
BLI API's dealing with nil terminated strings,
it avoids having to pass in `sizeof(value) - 1`.