scda: Write and read inline file sections

[tim-griesbach]

scda: Write and read inline file sections

This PR continues the implementation of the scda file format (cf. #197 and #193) by implementing fwrite_inline, fread_section_header for the case of an inline file section and fread_inline_data. Moreover, this PR contains in particular the following changes:

• Introduce a static function to generate the part of headers that always have the same structure,
• track the last fread_section_header call in the file context to be able to generate a suitable error code if the user does not follow the required reading workflow,
• generalize the macros for non-collective errors to handle non-collective code on a fixed but arbitrary rank and
• basic tests of the new scda functions.