Make `--gas-report` w/ `--json` output one JSON blob and add `contract_path` to output

[zerosnacks]

Component

Forge

Describe the feature you would like

Follow up of https://github.com/foundry-rs/foundry/pull/9063

Ref: https://github.com/foundry-rs/foundry/pull/9063#issuecomment-2411355213

the emitted json data loses the contract path completely, which is unfortunate as in projects with more than one contracts this information is actually quite important. Especially if multiple contracts have the same signatures it's becoming impossible to distinguish.

the emitted json is not valid json - each line for itself, yes, but the overall generated output is not(as it's missing separators and a bounding array). Imo the goal should be that piping forge test --gas-report --json > some.json, i receive a valid json i can post-process.

cc @sakulstra

Additional context

No response