Include comparison between vulnerability evaluations in minder summary

[gregfurman]

Please describe the enhancement

Currently there is a WIP (https://github.com/stacklok/minder/issues/1862) addition to minder reviews to include a summary comment that will always be edited atop the PR.

This will include some summary results on vulnerabilities and fixes found. However, I think it is important to include a point of comparison between the current results and previous ones.

This also brings about two questions:

• Should this compare with the HEAD of the PR?
• Should this compare with the previous evaluation results?

The summary data of the previous scan will be stored as an HTML comment in the body of the current top review -- functioning as metadata that can be parsed.

Example report below

Minder Vulnerability Report ⚠️

Minder found vulnerable dependencies in this PR. Either push an updated version or accept the proposed changes. Note that accepting the changes will include Minder as a co-author of this PR.

---

Vulnerability scan of 27d6810b:

📊 View Full Review

• 🐞 vulnerabilities: 1
• 🛠 fixes: 1

Package	Version	#Vulnerabilities	#Fixes	Patch Exists
mongodb	0.5.0	1	1	✅

⚖️ Comparison with abcdefgh

**Vulnerability comparison here**

Solution Proposal

Some options if we decide that a comparison is a good idea:

Compare using diff

Current has fewer vulns than target

Vulnerability scan of abcdefgh (vs 27d6810b):

+ 🐞 Vulnerabilities: 4 (-3)
+ 🛠 Fixes: 2 (-1)

Current has more vulns than target

Vulnerability scan of abcdefgh (vs 27d6810b):

- 🐞 Vulnerabilities: 0 (+1)
- 🛠 Fixes: 0 (+1)

Keep using codeblock

Vulnerability scan of abcdefgh (vs 27d6810b):

• 🐞 Vulnerabilities: 4 (-3)
• 🛠 Fixes: 1 (+0)

Describe alternatives you've considered

No response

Additional context

No response

Acceptance Criteria

No response

[lukehinds]

I love the new formatting @gregfurman !

[evankanderson]

@gregfurman -- did you fix this with #2171 ?

[evankanderson]

We still want to do the clever formatting trick with ```diff blocks...