Enhance plot_lcc_freq_bar Function to Accommodate n Land Cover Types

[dindiarto]

The plot_lc_freq function currently supports the comparison of land cover frequencies for two distinct time points (T1 and T2). This issue seeks to enhance the function to accommodate an arbitrary number (n) of time points.

As a guide for the proposed enhancements, we can refer to this implementation, which already accommodates n land cover types.
The enhancements would involve:

• Modifying the function arguments to accept a variable number of columns for time points. This could be done by replacing column_T1 and column_T2 with a single parameter that accepts a list of column names.

• Adapting the internal data processing logic to iterate over the list of time point columns. Particularly, this would affect the NA replacement, data reshaping, and max range calculation.

• Generating separate plots for each time point and concatenating them together. The code that generates the individual bar plots would need to be looped over the list of time point columns.

[dindiarto]

calc_lc_freq has accomodated n-Land Cover as an input