feat: expose the renderer interface

[aymanbagabas]

This adds the ability to use a custom renderer using a modified version of the existing renderer interface. This also keeps track of enabled capabilities and ensure they are turned off on program exit. It only turns off enabled capabilities rather.

The new API looks like:

// Renderer is the interface for Bubble Tea renderers.
type Renderer interface {
	// Close closes the renderer and flushes any remaining data.
	Close() error

	// Render renders a frame to the output.
	Render(string) error

	// SetOutput sets the output for the renderer.
	SetOutput(io.Writer)

	// Flush flushes the renderer's buffer to the output.
	Flush() error

	// InsertAbove inserts lines above the current frame. This only works in
	// inline mode.
	InsertAbove(string) error

	// Resize sets the size of the terminal.
	Resize(w int, h int)

	// Request a full re-render. Note that this will not trigger a render
	// immediately. Rather, this method causes the next render to be a full
	// Repaint. Because of this, it's safe to call this method multiple times
	// in succession.
	Repaint()

	// ClearScreen clear the terminal screen. This should always have the same
	// behavior as the "clear" command which is equivalent to `CSI 2 J` and
	// `CSI H`.
	ClearScreen()

	// SetMode sets a terminal mode on/off. The mode argument is an int
	// consisting of the mode identifier.
	// For example, to set alt-screen mode, you would call SetMode(1049, true).
	SetMode(mode int, on bool)

	// Mode returns whether the render has a mode enabled.
	// For example, to check if alt-screen mode is enabled, you would call
	// Mode(1049).
	Mode(mode int) bool
}

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This also introduces some performance gains by not writing unnecessary sequences on enable/disable terminal modes. For example, we always hide the cursor when the program runs, it doesn't make sense to write the sequence again when the model sends a HideCursor command, we already know it's hidden. Don't always disable mouse if it wasn't enabled in the first place.