Fix reconnection logic to not exhaust retries prematurely

[TMysliwiec]

This is a fix for: #481, which was just closed again, likely due to inactivity.

Problem:
The reconnection logic doesn't properly honor the reconnection interval. The interval starts counting from engine creation, not from when reconnection begins. If the engine runs for over 50 seconds (RECONNECT_ATTEMPTS × RECONNECT_INTERVAL), the reconnection loop immediately executes all attempts without waiting, causing it to fail after a couple of seconds. That is because we are using Tokio's default interval, which utilizes MissedTickBehavior::Burst. Any accumulated ticks will fire immediately.

rust-sdks/livekit/src/rtc_engine/mod.rs

Line 52 in 0699735

pub const RECONNECT_ATTEMPTS: u32 = 10;

Solution:
By changing the interval missed tick behavior to MissedTickBehavior::Delay, we can achieve the potentially initially desired await before making another reconnection attempt. That way, the reconnection window is significantly larger, thereby increasing the likelihood of reconnection.

Reproduction steps:
The problem is quite simple to reproduce. You need to run the basic_room example, wait a minute, disconnect the internet, and observe how fast the reconnection attempts are exhausted.

[CLAassistant]

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[davidzhao]

@TMysliwiec thank you for the contribution! could you sign the CLA so we can merge the fix?

[TMysliwiec]

Already signed it. Maybe it takes some time to process that? When I click on the button it says it is already signed.

[TMysliwiec]

@davidzhao not sure if there is anything more I can do in terms of the CLA. When I click recheck the status it reroutes me to this page and on their side it says it's already signed.
There is a lot of similar issues like that on the web so seems I am not alone on that one.

[TMysliwiec]

I think I have mixed commits and submit using my 2 accounts. Let me recreate the PR

[TMysliwiec]

@davidzhao created new one: #786