[REF-1705] Do not overwrite Var attributes during format

[masenf]

If the values given to format_cond are already Var, do NOT mutate the attributes since subsequent usages of the same Var may be adversely affected.

Add test cases for is_prop=True path of format_cond, where this bug was hiding.

Here is a repro case

import reflex as rx
import reflex.components.radix.themes as rdxt


class State(rx.State):
    val: str = ""


def index() -> rx.Component:
    print(repr(State.val))
    comp = rdxt.flex(
        # The following line exposes the bug: the radio group value gets formatted incorrectly.
        rdxt.text(rx.cond(State.val, State.val, "No Selection")),
        rdxt.text(State.val),
        rdxt.radio_group_root(
            rdxt.radio_group_item(value="1"),
            rdxt.radio_group_item(value="2"),
            rdxt.radio_group_item(value="3"),
            rdxt.radio_group_item(value="4"),
            value=State.val,
            on_value_change=State.set_val,
        ),
        rdxt.button("Clear", on_click=State.set_val("")),
        direction="column",
        justify="center",
        align="center",
        gap="2",
    )
    print(repr(State.val))
    return comp


app = rx.App()
app.add_page(index)

Check the output, the State.val repr should NOT change just because the value was used in an rx.cond.