Fix record_size_limit extension handling when resuming

As !879 (merged) seems to require some more work, this is a split-off for the 3.6.6 release. It fixes:

• resetting record_size_limit after resumption
• rejecting overlong extension

Checklist

• Code modified for feature
• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation updated / NEWS entry present (for non-trivial changes)

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTION.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code