Strformat symbol binding

[krux02]

• strformat.format is renamed to strformat.formatValue, so it does not clash with strutils.format.
• The (in my opinion complicated and weird logic) in the callFormat templates is removed entirely. formatValue has to follow the interface formatValue*(value: T; specifier: string; res: var string). Hacks to support alternative interfaces are removed.
• Libraries can overload formatValue to enable custom types within to be used in the & macro.
• Libraries have full control over the meaning of the specifier string for their own types.
• The changes above enable an implementation for the nim_glm types to be used in the & macro.
• fixes strformat doesn't work properly inside generics #7632
• the macro & is moved below the definition of formatValue, so that bindSym gets them all. Sorry that makes the diff harder to read, but it is important.

breaking change:

Custom types now need to overload formatValue explicity. It would be possible to provide a generic formatValue that is based on $, but I decided against it. Most importantly, when the generic formatValue does not exist, there is a really nice error message that tells the developer that there is a missing formatValue that should be implemented. I also did it, because it is not clear to me what to do with the specifier argument.

[krux02]

The test suid did already pass before I did a minor change.