fix: sync editor.wordSeparators and vim.iskeyword. closes #3166

[jpoon]

What this PR does / why we need it:

• Adds iskeyword as an overlap setting to editor.wordSeparators. As a result, the following will take precedence:

1. vim.iskeyword
2. if (1) is undefined, editor.wordSeparators
3. if (2) is undefined, then default value of @,48-57,_,128-167,224-235 is used

• This change removes the default value for iskeyword so unless users have explicitly configured this value, editor.wordSeparators will be used.

So in the standard use case where users were using the default values for iskeyword those folks will be moving from using this:

/\()\"':,.;<>~!@#$%^&*|+=[]{}`?-

to vscode's default for editor.wordSeparators

`~!@#$%^&*()-=+[{]}\|;:'",.<>/?

The two are the same set, but in different order so there should not be a change in behaviour. Note that if vim.iskeyword is set, it will override the value of editor.wordSeparators.

Which issue(s) this PR fixes
#3166

Special notes for your reviewer:

[jpoon]

Removing the breaking-change label as looking at the two sets, they are the exact same, just in different orders so we are good here :)