[Feature] Modify plot data series without having to pass the entire data

**Is your feature request related to a problem? Please describe.**
Right now, to modify a data series you need to call the `add_*_series()` function for the type of series and pass it all of the data to overwrite the existing data with.

This can be wasteful if e.g. you are adding just a few data points to a series with 1000s of elements.

**Describe the solution you'd like**
There could be a collection of functions in `dearpygui.core` that provide the ability to modify an existing data series without having to overwrite everything.

Possible operations to consider adding:
- Append a single value
- Insert a single value
- Delete a single value
- Append a collection of values
- Insert a collection of values
- Delete a range of values

Not all of the operations listed above need to be added, if any of them are impractical or undesirable for whatever reason. Probably the most important one would be to support appending a single value or a collection of values.