Fix/data viewer display

[Fred-Wu]

Closes #1463
Closes #1408

1. The fix disables JSON's default decimal rounding for all numeric values. AG Grid continues to use JS default formatting, which switches to scientific notation below 1e-6.

   1.54e-5 would appear as 0.0000154 in the data viewer instead of 0.
   1.54e-7 would appear as 1.54e-7 in the data viewer.

2. The fix adds one shared formatting function that calls R's format() generic to use each class's formatting method when displaying its values. If a class does not implement a format.xxx() method, R uses format.default() by default.

[eitsupi]

Could we also add a regression test for an S4 numeric subclass?
The new synthetic class test is S3, whereas lubridate::Period is an S4 class extending numeric, which is the exact shape that previously fell into the numeric-column branch.
A minimal synthetic S4 class would test the new is.object() behavior without adding lubridate as a dependency.

[Fred-Wu]

Could we also add a regression test for an S4 numeric subclass? The new synthetic class test is S3, whereas lubridate::Period is an S4 class extending numeric, which is the exact shape that previously fell into the numeric-column branch. A minimal synthetic S4 class would test the new is.object() behavior without adding lubridate as a dependency.

I will add a test for that. But the fix should be general for numeric values with an arbitrary class, which is based on both is.numeric() and is.object() checks. If both are TRUE, they will enter textColumn branch and values will get formatted based on the class's format() method.