Feat: Add ability to customize symbols

[wbthomason]

This PR adds the option to customize any subset of the kind symbols in a call to init. There are a few things to note:

• First, this PR necessarily removes the intentional code duplication, and does introduce a loop and (in the case of with_text = true) two concatenations. While this is less efficient than the original, this code should only run once (at LSP setup time) and is doing at most 50 concatenations, so the performance impact should be (imo) acceptable.
• Second, this PR does keep some intentional code duplication in having a separate loop for each of the with_text cases - this prevents the need to check the conditional on each iteration.

[onsails]

Oh, that was the next thing I was going to implement. Nice, thanks!