Multiple logical validators

[hrubaanna]

Current issue:

The application was crashing with two error types:
"The application panicked (crashed).

1. Message: Cannot start a runtime from within a runtime. This happens because a function (like block_on) attempted to block the current thread while the thread is being used to drive asynchronous tasks.
2. Message: core thread is not expected to stop: RecvError(())

Mulitple locations in block_handler.rs, spawned.rs -> everywhere with a block_on or similar blocking functions:
Location: mysticeti-core/src/block_handler.rs:476
Location: mysticeti-core/src/block_handler.rs:169
Location: mysticeti-core/src/block_handler.rs:229
Location: mysticeti/mysticeti-core/src/core_thread/spawned.rs:121
Location: mysticeti/mysticeti-core/src/core_thread/spawned.rs:106
Location: mysticeti/mysticeti-core/src/core_thread/spawned.rs:81

I converted many of these functions into asynchronous, which stopped the errors, but now either:

• the BlockHandler begins receiving txs from BlockGenerator channel OR;
• the NetworkSyncer is started and Core thread is started, allowing to Syncer trying to commit new blocks.