[Feature request]: Add ability to define enums without setting variable

Nobody has claimed this yet.

### How are you using the lua-language-server?

NeoVim

### Which OS are you using?

Linux

### What is the issue affecting?

Annotations

### Expected Behaviour

Enum fields are defined and shown when hovering over the variable they are assigned to.

### Actual Behaviour

Not all enum fields are picked up. The fields that are picked up are displayed as `unknown`.

### Reproduction steps

Not needed for a feature request.

### Additional Notes

When using Neovim, the standard library that comes with it is defined in files which use `any` a lot. An issue that I have ran into when trying to define an `enum` for a `table` that looks like the following is that it just won't work.

Table I am trying to define (this is what is show when hovering):

```lua
vim.log.levels: {
TRACE: integer = 0,
DEBUG: integer = 1,
INFO: integer = 2,
WARN: integer = 3,
ERROR: integer = 4,
OFF: integer = 5,
}
```

I have tried a couple of ways to define an enum to cover this:

```lua
-- Method 1
---@enum LogLevels
---| '0'
---| '1'
---| '2'
---| '3'
---| '4'
---| '5'

-- Method 2
---@enum LogLevels
---| TRACE = '0'
---| DEBUG = '1'
---| INFO = '2'
---| WARN = '3'
---| ERROR = '4'
---| OFF = '5'

-- Method 3
---@enum LogLevels
---| TRACE: 0
---| DEBUG: 1
---| INFO: 2
---| WARN: 3
---| ERROR: 4
---| OFF: 5

-- Method 4
---@enum LogLevels
---| TRACE: integer = 0 # Trace level
---| DEBUG: integer = 1 # Debug level
---| INFO: integer = 2 # Info level
---| WARN: integer = 3 # Warn level
---| ERROR: integer = 4 # Error level
---| OFF: integer = 5 # Off level
```

And then, when trying to set the variable to the `enum` `vim.log.levels`, I have done a couple of things as well:

```lua
-- Method 1
---@type LogLevels
M.levels = vim.log.levels --[=[@as LogLevels]=]

-- Method 2
---@type LogLevels
local tmp_levels = vim.log.levels --[=[@as LogLevels]=]
---@type LogLevels
M.levels = tmp_levels
```

When doing any of these, if I hover over `M.levels` only 3 of the fields are shown:

```lua
(field) M.levels: LogLevels {
ERROR: unknown,
INFO: unknown,
WARN: unknown,
}
```

I am aware that the following can be done to do something similar.
However, I would like to be able to add descriptions to fields and I would like to not see a table literal in the inlayhints.
Also, this won't work as a parameter type for a function because it would expect a table literal instead of an enum field.

This works for type declaration:

```lua
---@alias LogLevels { TRACE: 0, DEBUG: 1, INFO: 2, WARN: 3, ERROR: 4, OFF: 5 }

---@type LogLevels
M.levels = vim.log.levels
```

### Log File

Not needed for a feature request.

Start by reproducing the enum declaration and assignment examples in a Neovim/Lua-language-server setup, then trace how @enum annotations, type assignment, and hover output are handled. Done means enums can be declared without assigning a variable, retain named fields and descriptions, and work as the type of vim.log.levels and function parameters.

Written by the indexing model from the issue text.