New STR_FORMAT function

[oswaldobapvicjr]

This PR creates a new String function STR_FORMAT(format [, argument, ...]) which can be used to produce formatted strings. For example:

STR_FORMAT("Greetings from %s!", "Brazil")
Result: "Greetings from Brazil!"

"STR_FORMAT("%.2f %s", 11.1, "EUR")
Result: "11.10 EUR"

It can be useful to apply some formatting from numbers to strings.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[uklimaschewski]

I merged it, though I see a problem with the (non-) usage of a locale here (and also in the already existing date functions).
To fix this problems, I will introduce a configurable locale to the expression configuration.
This will also allow to get rid of the ugly static locale setting in the test.