CCIP-3711 modify README for foundry and remove HH references

contracts/README.md

@@ -15,31 +15,76 @@ $ npm install @chainlink/contracts --save
 @chainlink/contracts
 ├── src # Solidity contracts
 │   └── v0.8
-└── abi # ABI json output
-    └── v0.8
+│── abi # ABI json output
+│   └── v0.8
+└── gas-snapshots # gas metered results of available non-fuzz tests
 ```
 
 ### Usage
 
 The solidity smart contracts themselves can be imported via the `src` directory of `@chainlink/contracts`:
 
 ```solidity
-import '@chainlink/contracts/src/v0.8/AutomationCompatibleInterface.sol';
+import '@chainlink/contracts/src/v0.8/ChainSpecificUtil.sol';
 ```
 
-## Local Development
+## Foundry
+
+Chainlink supports Foundry testing for Solidity for its available products. Any new products or tests should only use Foundry
+in the future.
+
+### Installation
+
+Please see the [official docs](https://book.getfoundry.sh/getting-started/installation) for the latest installation guide
+
+The foundry version used by the project may be different than your locally installed version, which 
+can result in different test results, so a series of alias commands with `GNUMakefile` is offered to help ensure the correct version is available. Please ensure your system supports makefiles before running them.
 
-Note: Contracts in `dev/` directories are under active development and are likely unaudited. Please refrain from using these in production applications.
+Depending on your foundry-profile, you may need to install external dependencies from libraries such as Openzeppelin. 
+This can be done efficiently with `pnpm` as well
 
 ```bash
 # Clone Chainlink repository
 $ git clone https://github.com/smartcontractkit/chainlink.git
-# Continuing via pnpm
-$ cd contracts/
-$ pnpm
-$ pnpm test
+$ cd chainlink/contracts/
+# Download and install the correct foundry version.
+$ make foundry
+# Download external dependencies
+$ pnpm i
+# Compile and run all tests using the default profile.
+$ forge test
+```
+
+
+### CI
+
+The Foundry CI will build, run tests and check the gas usage of all test functions against the version controlled `.gas-snapshot` file.
+This snapshot should always be up-to-date and can be generated by running `make snapshot`. This will create a snapshot file in the current working dir, please make sure that you are in the root `chainlink/contracts` directory. 
+
+We do not track the gas results of fuzz-tests as to not introduce too much variability in the snapshot file between executions. Using `forge snapshot` is therefore not encouraged, as it will record the gas metered results of these-fuzz tests, which may not reproducible exactly by the CI. If you wish to view the results of these fuzz tests, we recommend using normal `forge test` instead. 
+
+```bash
+$ make snapshot # Run the test files without fuzz tests and record results.
+$ forge test # Run all tests, including fuzz.
+```
+
+### Configuration
+
+Foundry config lives in `foundry.toml` in the root, the docs can be found [here](https://book.getfoundry.sh/config/).
+The remapping of libraries, both from Foundry and NPM packages, is done in `remapping.txt`.
+
+### Profiles
+
+Different Chainlink projects are organized by folder and unique [Foundry Profiles](https://book.getfoundry.sh/reference/config/overview?highlight=profiles#profiles).
+Setting a profile can be used to restrict the compiler to specific files, reducing compilation time significantly. We
+recommend configuring this by setting your `FOUNDRY_PROFILE` environment variable to the profile which best fits your need.
+
+```bash
+$ export FOUNDRY_PROFILE=ccip # Set the profile to only apply only to CCIP specific contracts.
 ```
 
+The complete list of profiles and their associated tests can be found in the `foundry.toml` file.
+
 ## Contributing
 
 Please try to adhere to [Solidity Style Guide](https://github.com/smartcontractkit/chainlink/blob/develop/contracts/STYLE.md).