feat!: NNS-managed RPC providers

[rvanasa]

This PR makes significant changes to the EVM RPC canister to enable using NNS proposals in place of a trusted principal to add, remove, and update RPC providers.

Progress:

• [x] Refactor Provider struct for immutability
• [x] Remove per-provider cycles accounting in favor of decentralized ownership
• [x] Update JSON-RPC API configuration for default RPC providers
• [x] Change URL and header config to use {API_KEY} placeholder
• [x] Adjust URL / header validation logic
• [x] Include more tests for URL / header validation
• [x] Refactor to use ProviderId type alias
• [x] Implement post-upgrade actions to add, remove, and update one or more providers
• [x] Add new API key system
• [x] Remove stableSize and stableRead canister methods
• [x] Simplify principal authorization system
• [x] Remove authorize, deauthorize, and getAuthorized canister methods
• [x] Convert to using hard-coded RPC providers and service mappings
• [x] Add sanity checks for hard-coded providers and service-provider mappings
• [x] Remove FreeRpc auth
• [x] Remove PriorityRpc auth as well as getOpenRpcAccess and setOpenRpcAccess
• [x] Use a fixed number of subnet nodes (28) for all EVM RPC deployments
• [x] Remove PrincipalStorable struct
• [x] Include changes from dfinity/ic#1027
• [x] Include changes from dfinity/ic#1113
• [x] Add optional public_url to each provider
• [x] Refactor URLs and headers to use enum variants
• [x] Add demo flag to locally use EVM RPC canister without cycles payments, e.g. through Candid UI
• [x] Remove header validation in favor of overwriting default Content-Type header
• [x] Update state machine test runner logic to test new init/upgrade args
• [x] Update existing tests
• [x] Add unit tests for URL validation
• [x] Test API key insertion
• [x] Test simplified permission system
• [x] Update Rust and Motoko E2E tests
• [x] Add public URLs for all RPC providers

[rvanasa]

This PR should be ready to merge!

[rvanasa]

Thank you for the detailed review @gregorydemay! I'll merge this and then will make follow-up changes in separate PRs as mentioned.