Alias comments only show for strings and numbers

(Split from: https://github.com/LuaLS/lua-language-server/issues/2279)

Aliases have a feature where they can be multiline and you can write comments for different available values. However, this only works for string and numbers. For example in this code:

---@class TestClass

---@enum TestEnum
TestEnum = {
	TEST1 = 1,
	TEST2 = 2,
	TEST3 = 3,
}

---@alias TestAlias
---| 'TEST1' # TEST1 comment
---| 'TEST2' # TEST2 comment
---| 'TEST3' # TEST3 comment
---| TestClass # TestClass comment
---| TestEnum # TestEnum comment
---| TestEnum.TEST1 # TestEnum.TEST1 comment
---| 1 # TestNumber Comment

---@param test TestAlias
local function test(test)
end

test()

I get this

Reproduce the report in LuaLS with the alias example from the issue, then trace how alias comments are collected and displayed for string and numeric values. Check the same behavior for TestClass, TestEnum, and TestEnum.TEST1; done means comments appear for those alias values as they do for strings and numbers.