[rust-launcher] Add validation for LauncherConfig RPC parameters

[barakeinav1]

Context

Follow-up from PR #2326 (port node launcher to Rust). Tracked in #2598.

Problem

In crates/tee-launcher/src/types.rs (lines 62-66), rpc_request_timeout_secs, rpc_request_interval_secs (u64), and rpc_max_attempts (u32) have no bounds checking. Zero values cause silent failures in the retry logic.

Action

Either:

• Use NonZeroU64 / NonZeroU32 types, or
• Add a Config::validate() method called after deserialization
• Consider also validating that rpc_request_interval_secs <= rpc_request_timeout_secs