Fixes asterisk notation for mpes reader

[domna]

This PR should enable proper collection of axis names from xarray.
We use an asterisk for this to create key-value pairs:

"/ENTRY[entry]/data": {
    "@axes": "@data:dims",
    "AXISNAME_indices[@*_indices]": "@data:*.index",
    "@signal": "data",
    "data": "@data:data",
    "data/@units": "counts",
    "AXISNAME[*]": "@data:*.data",
    "AXISNAME[*]/@units": "@data:*.unit",
    "energy/@type": "binding"
  }

, which creates, e.g., AXISNAME[energy] = @data:energy.data for all names in the data array.
We however, would like to be able to rename the key manually or enter a different value for the key. So if either the value or the key are present in the file the automatism should not write this particular entry. This manual overwriting does not work properly and needs to be fixed.

[coveralls]

Pull Request Test Coverage Report for Build 7868474982

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 44.584%

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Totals
Change from base Build 7830110631:	0.0%
Covered Lines:	4906
Relevant Lines:	11004

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💛 - Coveralls

[domna]

This will be fixed in FAIRmat-NFDI/pynxtools-mpes#1