Add toString() method for ForwardingInputFile and ForwardingOutputFile

[findinpath]

Description

While dealing with failure scenarios, it is helpful to see what file is causing the issue

io.trino.testing.QueryFailedException: Failed to read file: ForwardingInputFile{inputFile=s3://test-bucket/tpch/corrupt_table_y4fjmbitkt-a9f1d9ebba684cd8b19ddcdc58725c68/metadata/00002-c9681ed7-843a-4484-92ed-606ef7c07e75.metadata.json}

instead of

io.trino.testing.QueryFailedException: Failed to read file: io.trino.plugin.iceberg.fileio.ForwardingInputFile@2cdc22bb

Release notes

(x) This is not user-visible or docs only and no release notes are required.
( ) Release notes are required, please propose a release note for me.
( ) Release notes are required, with the following suggested text: