Add strfmt macro function instead of changing strformat

[fishface60]

Identify the Bug or Feature request

fixes #5226

Description of the Change

Macros depend on the behaviour of strformat bypassing interpolations if there are no passed parameters, contrary to documentation, so strformat's behaviour can't be changed.

Instead we can introduce a new strfmt macro function with more well-defined behaviour of always handling String.format escapes and also not processing the interpolations if you use both interpolations and positional formatting.

Possible Drawbacks

Having both strformat and strfmt is confusing. strformat should be deprecated but it is slightly faster if you are only interpolating strings.

Documentation Notes

strfmt behaves like strformat is documented to.

strfmt and strformat should share a wiki page and behaviours where strformat diverges should be documented, i.e.

1. Formatting Data Type

   NOTE: These format specifiers are ignored if strformat is used and no positional arguments are provided, so %% and %n format specifiers are ignored. Use strfmt if format specifiers are required without positional arguments.

2. Formatting by Embedding Variables

   NOTE: The contents of the variables are interpreted as format specifiers if strformat is used and positional arguments are provided, so a string containing the value "100%" may be interpreted as a format string and cause errors. Use strfmt if embedded variables and positional arguments are both used and the variables may contain % characters.

Release Notes

• Added strfmt macro function to replace strformat so %% and %n format specifiers may be used without positional parameters and allow mixing Variable Embedding with positional formatting. strformat is retained with the previous behaviour for compatibility with existing macros.

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This change is 

[fishface60]

This will conflict with #5343 when release-1.17 is merged back into develop.

If you would like to do that first I can rebase this change on top.

[kwvanderlinde]

Created #5351 to merge release-1.17 first.

[cwisniew]

Created #5351 to merge release-1.17 first.

And it has now been merged

[fishface60]

Thanks, rebased.