sits_uncertainty_sampling - slow and not performing as expected

[gilbertocamara]

The sits_uncertainty_sampling() function was very slow and was not working in expected. In a case where there were many points with the same value of uncertainty, the function was not shuffling the resulting tibble randomly.

This bug is fixed in version 1.5.2. Now, all values are read to memory using terra and the samples tibble is shuffled randomly as expected.