feat: Better border configuration.

Started adding `resolve` which will allow you to do some really nice
stuff easily with options to get the window options from a variety of
inputs.

You can see how we do it in pickers.lua for borders & borderchars
currently.

lua/telescope/config/resolve.lua

@@ -0,0 +1,155 @@
+
+--[[
+
+Ultimately boils down to getting `height` and `width` for:
+- prompt
+- preview
+- results
+
+No matter what you do, I will not make prompt have more than one line (atm)
+
+Result of `resolve` should be a table with:
+
+{
+  preview = {
+    get_width = function(self, max_columns, max_lines) end
+    get_height = function(self, max_columns, max_lines) end
+  },
+
+  result = {
+    get_width = function(self, max_columns, max_lines) end
+    get_height = function(self, max_columns, max_lines) end
+  },
+
+  prompt = {
+    get_width = function(self, max_columns, max_lines) return 1end
+    get_height = function(self, max_columns, max_lines) end
+  },
+}
+
+!!NOT IMPLEMENTED YET!!
+
+height =
+    1. pass between 0 & 1
+        This means total height as a percentage
+
+    2. pass a number > 1
+        This means total height as a fixed number
+
+    3. {
+        previewer = x,
+        results = x,
+        prompt = x,
+    }, this means I do my best guess I can for these, given your options
+
+    4. function(max_rows)
+        -> returns one of the above options
+        return max.min(110, max_rows * .5)
+
+        if columns > 120 then
+            return 110
+        else
+            return 0.6
+        end
+
+width =
+    exactly the same, but switch to width
+
+
+{
+    height = 0.5,
+    width = {
+        previewer = 0.25,
+        results = 30,
+    }
+}
+
+https://github.com/nvim-lua/telescope.nvim/pull/43
+
+After we get layout, we should try and make top-down sorting work.
+That's the next step to scrolling.
+
+{
+    vertical = {
+    },
+    horizontal = {
+    },
+
+    height = ...
+    width = ...
+}
+
+
+
+--]]
+
+local get_default = require('telescope.utils').get_default
+
+local resolver = {}
+
+local percentage_resolver = function(selector, percentage)
+  assert(percentage <= 1)
+  assert(percentage >= 0)
+
+  return function(...)
+    return percentage * select(selector, ...)
+  end
+end
+
+resolver.resolve_percentage_height = function(percentage)
+  return percentage_resolver(3, percentage)
+end
+
+resolver.resolve_percentage_width = function(percentage)
+  return percentage_resolver(2, percentage)
+end
+
+--- Win option always returns a table with preview, results, and prompt.
+--- It handles many different ways. Some examples are as follows:
+--
+-- -- Disable
+-- borderschars = false
+--
+-- -- All three windows share the same
+-- borderchars = { '─', '│', '─', '│', '┌', '┐', '┘', '└'},
+--
+-- -- Each window gets it's own configuration
+-- borderchars = {
+--   preview = {...},
+--   results = {...},
+--   prompt = {...},
+-- }
+--
+-- -- Default to [1] but override with specific items
+-- borderchars = {
+--   {...}
+--   prompt = {...},
+-- }
+resolver.win_option = function(val, default)
+  if type(val) ~= 'table' or vim.tbl_islist(val) then
+    if val == nil then
+      val = default
+    end
+
+    return {
+      preview = val,
+      results = val,
+      prompt = val,
+    }
+  elseif type(val) == 'table' then
+    assert(not vim.tbl_islist(val))
+
+    local val_to_set = val[1]
+    if val_to_set == nil then
+      val_to_set = default
+    end
+
+    return {
+      preview = get_default(val.preview, val_to_set),
+      results = get_default(val.results, val_to_set),
+      prompt = get_default(val.prompt, val_to_set),
+    }
+  end
+end
+
+return resolver