Improve reporting and summation checks for NGFS6

[lecfab]

Purpose of this PR

• Addressing some https://github.com/remindmodel/development_issues/issues/815 through piamInterfaces

Parent variable	Reporting	Summation
Investment|Energy Supply	updated Liquids to new name
Population 2		added missing obesity
Final Energy|Residential and Commercial|Gases	remove duplicate
Final Energy|Residential and Commercial|Liquids	remove duplicate
...

Checklist:

• I did not use Excel to open csv files or checked that no side-effects occur (changed values, many new quotation marks, …)
• I added any renamed piam_variable to renamed_piam_variables.csv to guarantee backwards compatibility.
• For REMIND variables, I used |+| notation consistently. This can be achieved automatically with updatePlusUnit().

It is recommended to have a look at the tutorial before submission.