test: use --isolate for test

[ChefMist]

This PR migrate forge test to forge test --isolate.

From https://book.getfoundry.sh/reference/cli/forge/test - on what --isolate flag does

      --isolate
          Whether to enable isolation of calls. In isolation mode all top-level calls are executed
          as a separate transaction in a separate EVM context, enabling more precise gas accounting
          and transaction state changes

Context

1. --isolate will give us more accurate gas estimation as each call will now include a new transaction (21k) gas overhead
2. As we are using transient storage/ transient load, using --isolate will ensure that we don't use the tstore value in previous call.
3. It will also allow us to measure gas more accurately and see the benefit of transient storage in <WIP> feat: set reserveOf transient #33 where we no longer update reserveOfVault

[chefburger]

This seems a bit counter-intuitive to me. Just to confirm, does that mean:

1. Both storageLib.tstore(1, 2); and uint256 val = storageLib.tload(1); are separate txs
2. But if there are some external calls inside for example storageLib.tload it will behave like normal function call instead of stacking up another new tx

[ChefMist]

1. Both storageLib.tstore(1, 2); and uint256 val = storageLib.tload(1); are separate txs

Yes, they will run as seperate transaction which is why tload(1) will return 0 not 2 if you run test with forge test --isolate

2. If there are more external calls inside for example storageLib.tload it will behave like normal function call instead of stacking up another new tx

Yes. the seperate transaction is only from top level call.

Do you have a recommendation for the comment on the test or assert error message so it can be clearer? we can update to it

[chefburger]

ehhh, maybe we can mention it in README or FAQ somewhere. That should avoid most unnecessary debugging if someone encounters it 😂

[ChefMist]

updated readme with details 😁

[chefburger]

lgtm