[feat] generics: capture types with backticks

[jpeletier]

This PR modifies the generics capture system to allow to capture types out of the type of the parameter passed, in addition to being able to pass the type as a string which is the way it currently works:

Currently:

---@class Vehicle
local Vehicle = {}

---@class VehicleColor
local VehicleColor = {}

---@generic T
---@param class `T`Color # the type is captured using `T`
---@return T       # T becomes class + "Color"
local function getItemColor(class) end

-- obj: is of type VehicleColor
local obj = getItemColor("Vehicle")

Now, the following is also possible:

---@class Vehicle
local Vehicle = {}

---@class VehicleColor
local VehicleColor = {}

---@generic T
---@param class `T`Color # the type is captured using `T`
---@return T       # T becomes typeof(class) + "Color"
local function getItemColor(class) end

---@type Vehicle
local someVehicle = {}

-- obj: is of type VehicleColor
local obj = getItemColor(someVehicle)

-- obj2: is of type VehicleColor
local obj2 = getItemColor("Vehicle")

Therefore, it is possible to pass a literal string that happens to be a type name like before, or otherwise pass an expression that evaluates to a type and that type will be captured with backticks. This allows to construct typings for functions that return different types that depend on the type of the object passed.