fix(gomod): add -modfile flag for non-default go.mod filenames

[rogercoll]

Changes

Adds the -modfile argument if the target Go modules file is not go.mod. See failure example: open-telemetry/opentelemetry-ebpf-profiler#1220

When using managerFilePatterns to manage non-standard go.mod files (e.g. tools.mod), the go commands (get, mod tidy, mod vendor) now include the -modfile flag so they operate on the correct module file instead of defaulting to go.mod in the working directory

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