Cairo-lang

**Starknet**
* Use the [rust blockifier](https://github.com/starkware-libs/blockifier) and [LambdaClass's Cairo VM](https://github.com/lambdaclass/cairo-vm) to accelerate the sequencer's time to handle transactions
* Support version [2.0.0](https://github.com/starkware-libs/cairo/releases/tag/v2.0.0) of the Cairo compiler
* Replace the `PENDING` status of transactions to `ACCEPTED_ON_L2` - once a transaction is in that status it means that it will be included in a block (this applies to transactions - blocks still have the PENDING status)
* Add an experimental `get_block_hash` syscall (we plan to review how useful this syscall is, so treat it as experimental. We recommend using it *only in upgradable contracts*)
* Change HTTP error code from 500 to 400 on API errors

**Starknet**
* Use the [rust blockifier](https://github.com/starkware-libs/blockifier) and [LambdaClass's Cairo VM](https://github.com/lambdaclass/cairo-vm) to accelerate the sequencer's time to handle transactions
* Support version [2.0.0](https://github.com/starkware-libs/cairo/releases/tag/v2.0.0-rc5) of the Cairo compiler
* Replace the `PENDING` status of transactions to `ACCEPTED_ON_L2` - once a transaction is in that status it means that it will be included in a block (this applies to transactions - blocks still have the PENDING status)
* Add an experimental `get_block_hash` syscall (we plan to review how useful this syscall is, so treat it as experimental. We recommend using it *only in upgradable contracts*)

**Starknet**:
* Allow the use of Cairo 1.0 on Starknet mainnet
* Update Sierra->Casm compiler version to 1.1.0. Note that contracts that were compiled with v1.0.0 cannot be declared in this version. However, if they were already declared, they can still be used, and more instances can be deployed

**Starknet**:
* Allow the use of Cairo 1.0 on Starknet mainnet
* Update Sierra->Casm compiler version to 1.1.0-rc0. Note that contracts that were compiled with v1.0.0 cannot be declared in this version. However, if they were already declared, they can still be used, and more instances can be deployed

Minor bug fix in the Starknet CLI

**Starknet**:
* Upgrade Cairo 1.0 version to `v1.0.0-rc0`
* Charged transaction fee is now based on an *average* Ethereum gas price instead of a single sample (estimation API is unaffected)
* API changes:
* Remove the state root in `get_state_update` for pending blocks to allow faster responses in future versions
* Testing framework:
* Allow declaring (and interacting with) Cairo 1.0 contracts.
* Currently, the Cairo 1.0 ABI is not supported yet, so a Cairo 0 ABI should be supplied to `declare()` manually.
* Split `deploy()` to two phases declare and deploy: `deprecated_declare()` (for Cairo 0 contract) or `declare()` (for Cairo 1.0 contracts) and `deploy()` (for both)
* Add current block hash to the Starknet Core contract (currently not verified by the Starknet OS):
* **Breaking change**: The `LogStateUpdate` event's data is changed to include `blockHash`

**Other changes**:
* Change build system from CMake to bazel