Project custom scales are displayed with scientific notation

[SebastienPeillet]

Describe the bug

Using the Project Predefined Scales feature, it appears that denominator are displayed with scientific notation ( like 1:4.5e+06). Apart the fact that I believe that scales never use scientific notation, it also causes bugs because internationalization is not fully used in this part of the code.

Consequence :

• project scales combo box is not working for scientific value
• importing new predefined scales in project properties, it will not recognized scales that are already defined to avoid to import it twice ("1:1000000" will not be equal to "1:1e+06")

How to Reproduce

1. Go to Project Properties > General > Project Predefined Scales
2. Import or add scale with high denominator (like 4500000), scales are displayed right.
3. Close and go back to Project Properties, 4500000 are now displayed as 4.5e+06
4. Try adding again 4500000 as denominator, it works.

And futhermore the scale combo box doesn't work in the project

QGIS and OS versions

QGIS version	3.12.3-București	QGIS code revision	8234261
Compiled against Qt	5.12.4	Running against Qt	5.12.4
Compiled against GDAL/OGR	2.4.2	Running against GDAL/OGR	2.4.2
Compiled against GEOS	3.7.2-CAPI-1.11.2	Running against GEOS	3.7.2-CAPI-1.11.2 b55d2125
Compiled against SQLite	3.29.0	Running against SQLite	3.29.0
PostgreSQL Client Version	12.3 (Ubuntu 12.3-1.pgdg19.10+1)	SpatiaLite Version	5.0.0-beta0
QWT Version	6.1.4	QScintilla2 Version	2.10.4
Compiled against PROJ	5.2.0	Running against PROJ	Rel. 5.2.0, September 15th, 2018
OS Version	Ubuntu 19.10	This copy of QGIS writes debugging output.
Active python plugins	processing; db_manager

[rduivenvoorde]

@SebastienPeillet this issue can be closed, yes?

[SebastienPeillet]

Yes ! I thought it was automatically closed if the issue code were in the PR title...