Improve YAML anchor names

Currently the RapidYAML text format names anchor sequentially, see https://github.com/SymbiFlow/python-fpga-interchange/blob/3809a19f2f9cf80f014e439f9ae8643543c4519f/fpga_interchange/rapidyaml_support.py#L87

To aid readability of the text formats, the anchor names should incorporate some additional information. For example, rather than `id001` for a port anchor, `idXXX_port_` would be useful. To avoid exploding the file size, names should be truncated. Leaving the counter in the front avoids needing to de-duplicate names.