chore: migrate from git submodules to npm workspaces monorepo structure

[Chaitu-Tatipamula]

Migrate from Git Submodules to NPM Workspaces Monorepo

Summary

Migrates the Filecoin Services project from git submodules to a unified npm workspaces monorepo structure to improve developer experience and simplify dependency management.

Changes

• Remove git submodules and service_contracts/ directory
• Consolidate packages into unified monorepo with npm workspaces
• Centralize dependencies using npm for all packages except fvm-solidity
• Single Foundry project with unified build/test system
• Consolidated Makefile with 50+ targets for all development needs
• Updated GitHub workflows to work with new monorepo structure
• ABI extraction system compatible with new structure

Resolves #229

[wjmelements]

We have a nice modular codebase. Submodules are great. Monorepos are a burden in minor ways.

1. The tests are all run for everything every time. This wastes money and developer time. Developers may workaround by running fewer tests, but CI will not.
2. Reusing our modular contracts such as FilecoinPayV1 for other services is more difficult with monorepos. Their build and install times are longer, though they can sometimes workaround by undoing this change on their own fork.
3. Modular code in monorepos degrades into interdependent code, causing import cycles.
4. Monorepos have unbounded scope and so absorb everything they touch. There is no limiting principle preventing us, for example, from bringing synapse-sdk in here too. Our future services would probably also accumulate here.
5. Migration eliminates the git blame and git log which are helpful for digging up context and rationale.
6. The likelihood of merge conflicts and other incompatible changes is higher when the whole team is working at the same time on the same repo. At scale this can create a chokepoint and a merge backlog that can grow faster than it takes to run the tests.

I'm not convinced that the benefits outweigh the costs.

[rvagg]

@redpanda-f is tackling this one now, needs greater coordination across our team unfortunately so we'll have to work on it as a short multi-person sprint.