Handle root path '.' correctly in JSON.OBJLEN command

[JyotinderSingh]

The current implementation of JSON.OBJLEN does not correctly handle the root path '.'. This needs to be fixed to align with Redis behavior.

Current behavior: When using JSON.OBJLEN doc ., the library is unable to parse it and returns an error.

Expected behavior: JSON.OBJLEN doc . should return the length of the complete parent object, consistent with Redis behavior.

Additional context:

• This issue was identified in PR #593: https://github.com/DiceDB/dice/pull/593#discussion_r1761191999
• After implementation, appropriate tests should be added or updated in integration_tests/commands/json_test.go

Tasks:

• [ ] Implement the fix in evalJSONOBJLEN function
• [ ] Add or update tests to cover this scenario
• [ ] Ensure the fix doesn't introduce any regressions

[AshikBN]

@JyotinderSingh pls assign this to me.

[JyotinderSingh]

@JyotinderSingh pls assign this to me.

Assigned.

[HassanAarzoo]

@AshikBN Are you working on this? If not I would like to pick this up

[AshikBN]

i have not yet, you can start if you are interested @JyotinderSingh Can this be assigned to @HassanAarzoo Please

[kapishmalik]

@JyotinderSingh I am also interested to work on this issue