Replace Tasks generic with Box<dyn TaskExecutor>

[mattsse]

Describe the feature

currently we have a few places where we use Tasks as generic,
we can get rid of this by using Box<dyn>

including:

reth/crates/node/builder/src/builder/mod.rs

Line 185 in 6688078

pub const fn with_launch_context(self, task_executor: TaskExecutor) -> WithLaunchContext<Self> {

Additional context

No response

[estensen]

Taking a small break from #10749, pls assign me this one

[mattsse]

lets focus on the nodebuilder first, this could potentially flag a few limitations in the launch impls

[mattsse]

for example, I think this isn't part of the trait

reth/crates/tasks/src/lib.rs

Line 494 in 6688078

pub fn spawn_critical_with_graceful_shutdown_signal<F>(

actually, perhaps we hold off on NodeBuilder first and try tackling the generics in the rpc stack

[estensen]

Sorry, won't have the bandwidth this week. Feel free to assign to someone else.