Support --ir-minimum flag for forge coverage

[hudsonhrh]

Problem

The coverage job runs forge coverage which disables via_ir for accurate instrumentation. However, projects that use IR-only features (e.g., calldata[] calldata to storage copying) fail to compile without the IR pipeline:

Error (1834): Copying of type struct IExecutor.Call calldata[] calldata to storage
is not supported in legacy (only supported by the IR pipeline).

This results in an empty coverage report (0/0 for all metrics).

Proposed Solution

Add an optional coverage-ir-minimum boolean input (default false). When enabled, pass --ir-minimum to forge coverage, which enables viaIR with minimal optimization — enough for IR-dependent code while still producing accurate coverage.

coverage-ir-minimum:
  description: 'Pass --ir-minimum to forge coverage for projects requiring the IR pipeline'
  type: boolean
  default: false

Then in the coverage step:

if [[ "${{ inputs.coverage-ir-minimum }}" == "true" ]]; then
  forge coverage --ir-minimum 2>&1 | tee coverage-raw.txt
else
  forge coverage 2>&1 | tee coverage-raw.txt
fi

Context

Encountered in POP when enabling run-coverage: true. The forge coverage warning itself suggests this flag:

If you encounter "stack too deep" errors, consider using --ir-minimum which enables viaIR with minimum optimization resolving most of the errors