Introduce interoperability_getMainchainID endpoint

[sitetester]

What was the problem?

This PR resolves #8309

How was it solved?

Endpoint introduced

How was it tested?

Test cases added

[codecov]

Codecov Report

Merging #8758 (9fe727c) into release/6.0.0 (970b641) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 9fe727c differs from pull request most recent head c2160c6. Consider uploading reports for the commit c2160c6 to get more accurate results

Additional details and impacted files

@@              Coverage Diff               @@
##           release/6.0.0    #8758   +/-   ##
==============================================
  Coverage          83.31%   83.32%           
==============================================
  Files                594      594           
  Lines              22312    22315    +3     
  Branches            3291     3289    -2     
==============================================
+ Hits               18589    18593    +4     
+ Misses              3723     3722    -1     

Files Changed	Coverage Δ
...k/src/modules/interoperability/sidechain/module.ts	95.83% <ø> (ø)
framework/src/modules/interoperability/schemas.ts	100.00% <100.00%> (ø)
...src/modules/interoperability/sidechain/endpoint.ts	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

[mitsuaki-u]

As @shuse2 commented logic should be in sidechain endpoint and additionally update module.ts -> metadata -> endpoints with any required schemas