Work around failures in ENA XML retrieval to still produce useful info

[pinin4fjords]

Sometimes with ffq the ENA calls fail, like this:

 % ffq SRR12215634 
[2023-07-17 11:47:40,590]    INFO Parsing run SRR12215634
[2023-07-17 11:47:40,756]   ERROR 404 Client Error:  for url: https://www.ebi.ac.uk/ena/browser/api/xml/SRR12215634/
[2023-07-17 11:47:40,757]   ERROR 'NoneType' object has no attribute 'text'
usage: ffq [-h] [-o OUT] [-l LEVEL] [--ftp] [--aws] [--gcp] [--ncbi] [--split] [--verbose] [--version] IDs [IDs ...]
ffq: error: For possible failure modes, please see https://github.com/pachterlab/ffq#failure-modes

This is down to upstream errors at the ENA: https://www.ebi.ac.uk/ena/browser/view/SRR12215634 ,

What I'd really like is for ffq to do what it can without the ENA info. In this PR I illustrate that for runs. With these changes the above failing call now produces a useful response lacking only the specific things that come from ENA:

{
    "SRR12215634": {
        "accession": "SRR12215634",
        "experiment": null,
        "study": "SRP271756",
        "sample": "SRS7001069",
        "title": null,
        "attributes": {},
        "files": {
            "ftp": null,
            "aws": [
                {
                    "accession": "SRR12215634",
                    "filename": "C6_3_Pre_possorted_genome_bam.bam.1",
                    "filetype": "bam",
                    "filesize": null,
                    "filenumber": 1,
                    "md5": null,
                    "urltype": "aws",
                    "url": "s3://sra-pub-src-18/SRR12215634/C6_3_Pre_possorted_genome_bam.bam.1"
                },
                {
                    "accession": "SRR12215634",
                    "filename": "C6_3_Pre_possorted_genome_bam.bam.1",
                    "filetype": "bam",
                    "filesize": null,
                    "filenumber": 1,
                    "md5": null,
                    "urltype": "aws",
                    "url": "https://sra-pub-src-2.s3.amazonaws.com/SRR12215634/C6_3_Pre_possorted_genome_bam.bam.1"
                },
                {
                    "accession": "SRR12215634",
                    "filename": "SRR12215634",
                    "filetype": "sra",
                    "filesize": null,
                    "filenumber": 1,
                    "md5": null,
                    "urltype": "aws",
                    "url": "https://sra-pub-run-odp.s3.amazonaws.com/sra/SRR12215634/SRR12215634"
                },
                {
                    "accession": "SRR12215634",
                    "filename": "SRR12215634.lite.1",
                    "filetype": "sra",
                    "filesize": null,
                    "filenumber": 1,
                    "md5": null,
                    "urltype": "aws",
                    "url": "s3://sra-pub-zq-3/SRR12215634/SRR12215634.lite.1"
                }
            ],
            "gcp": [
                {
                    "accession": "SRR12215634",
                    "filename": "SRR12215634.lite.1",
                    "filetype": "sra",
                    "filesize": null,
                    "filenumber": 1,
                    "md5": null,
                    "urltype": "gcp",
                    "url": "gs://sra-pub-zq-7/SRR12215634/SRR12215634.lite.1"
                }
            ],
            "ncbi": [
                {
                    "accession": "SRR12215634",
                    "filename": "SRR12215634.lite.1",
                    "filetype": "sra",
                    "filesize": null,
                    "filenumber": 1,
                    "md5": null,
                    "urltype": "ncbi",
                    "url": "https://sra-downloadb.be-md.ncbi.nlm.nih.gov/sos4/sra-pub-zq-1/SRR012/12215/SRR12215634/SRR12215634.lite.1"
                }
            ]
        }
    }
}

Similar changes could be made to the other parse_x functions.