soroban-cli: Remove ALL RPC Related Code and Workflows

[stellarsaur]

What

Related to the Soroban RPC/CLI repo split.

This PR removes all Soroban RPC integration tests, workflows, crates, and code. In fact, this repo now doesn't use Golang at all. Specifically:

• Removed all code under cmd/soroban-rpc/ including integration tests
  • soroban-rpc repo will be responsible for integration tests since the integration tests in cmd/soroban-rpc/internal/test are for the functionality of Soroban RPC
• Removed Soroban RPC & Golang related workflows
• Removed Soroban RPC & Golang related Makefile commands
• Updated check_dependencies script
• Use soroban-rpc crate from soroban-rpc repo instead
• Update e2e.yml system test workflow to checkout Soroban RPC from soroban-rpc

Why

Now that we've functionally split the repos, this PR cleans up any remaining references to Soroban RPC in the soroban-tools repo. The soroban-rpc repo should be responsible for all RPC related code instead of this repo.

[leighmcculloch]

The README needs updating too.