spec: add muxed_decode vectors for edge ids and invalid case

[Obiajulu-gif]

This pull request expands the test coverage in spec/vectors.json by adding new test cases for muxed address decoding, especially covering edge cases and boundary values, and improves the formatting for readability. The most significant changes are grouped below:

New muxed address decode test cases

• Added test cases for decoding muxed addresses with boundary and edge values, including id=0, id=1, id=2^53, id=2^53+1, and id=2^64-1, to verify correct handling of precision and maximum values.
• Added a negative test case to ensure decoding fails with an invalid muxed address, verifying error handling.

Improved formatting for test vectors

• Reformatted all tags arrays to multi-line for consistency and readability across the file. [1] [2] [3] [4] [5] [6] [7]
• Updated object formatting in error contexts and normalization fields to use multi-line style, improving clarity. [1] [2]
  Closes Add muxed_decode vectors to spec/vectors.json #36