chore: replace frequenty used dict literals with data classes

[willmurphyscode]

For example:

vunnel/src/vunnel/utils/vulnerability.py

Lines 16 to 27 in c615dca

	vulnerability_element = {
	"Vulnerability": {
	"Severity": None,
	"NamespaceName": None,
	"FixedIn": [],
	"Link": None,
	"Description": "",
	"Metadata": {},
	"Name": None,
	"CVSS": [],
	},
	}

gets copy.deepcopy-ed around a lot, as a template for a dict literal. The code would be cleaner and have more useful type hinting if this were replaced with a data class.

Examples of copying

vunnel/src/vunnel/utils/oval_parser.py

Lines 160 to 170 in c615dca

	v = copy.deepcopy(vulnerability_element)
	ns_name = config.ns_format.format(re.search(config.platform_version_pattern, platform_element.text).group(1))
	v["Vulnerability"]["NamespaceName"] = ns_name
	v["Vulnerability"]["Severity"] = severity or ""
	v["Vulnerability"]["Metadata"] = (
	{"Issued": issued, "Updated": updated, "RefId": ref_id} if updated else {"Issued": issued, "RefId": ref_id}
	)
	v["Vulnerability"]["Name"] = name
	v["Vulnerability"]["Link"] = link
	v["Vulnerability"]["Description"] = description

and

vunnel/src/vunnel/providers/wolfi/parser.py

Lines 103 to 109 in c615dca

	vuln_dict[vid] = copy.deepcopy(vulnerability.vulnerability_element)
	vuln_record = vuln_dict[vid]
	reference_links = vulnerability.build_reference_links(vid)
	# populate the static information about the new vuln record
	vuln_record["Vulnerability"]["Name"] = str(vid)
	vuln_record["Vulnerability"]["NamespaceName"] = self.namespace + ":" + str(release)

[willmurphyscode]

We want to make sure that whatever solution we use is not vulnerable to crashing because a field is added, so maybe skipping straight to data classes is the wrong approach. I'll research some additional approaches.