Fix vulnerabilities in dependencies

[Muximize]

Description

Resolves 417 instances of 14 vulnerabilities in multiple versions of these 10 (transitive) dependencies:

Azure.Identity                   
Microsoft.Identity.Client        
Newtonsoft.Json                  
Npgsql                           
SixLabors.ImageSharp             
System.Formats.Asn1              
System.Net.Http                  
System.Security.Cryptography.Xml 
System.Text.Json                 
System.Text.RegularExpressions   

These stats are only for the framework solution but the modules where also fixed. These where found using:

dotnet list package --vulnerable --include-transitive

Notes

Because it gets annoying to keep having to fix these in our project, I thought maybe I should fix it at the source 😇

Instead of just updating the vulnerable package versions, I did some cleanup to reduce the amount of transitive dependencies and to make the process of updating them easier in the future:

• Some vulnerabilities are only present in the netstandard2.0 and netstandard2.1 targets of some dependencies. Because ABP 8 requires net8.0 anyway, I assume those targets can be safely dropped as an easy fix.
• The AssetTargetFallback can then be dropped from projects too.
• There are bunch of unused dependencies that I removed, but there might be more of them.
• Because IdentityServer4 is deprecated, there is no fix for its vulnerability. According to Announcement of plan to replace the IdentityServer #11989 it should have been removed by now as OpenIddict became the default in ABP 6.
• I also updated all other outdated dependencies I could find.

[CLAassistant]

All committers have signed the CLA.

[Muximize]

I rebased this on latest dev to fix a merge conflict.

[MichelZ]

Great initiative, I was just going to open an issue because of transitive package vulnerabilities that I'd like to see fixed 👍

[Muximize]

@maliming I see now ABP is usually quite conservative in updating dependencies, so maybe you can skip the last commit, or cherry pick what you like in this PR.

[maliming]

Thanks @Muximize

We will continue to support the netstandard2.0 and netstandard2.1. And packages have been upgraded in #20960

I will cherry-pick your commit to a new Pull Request. 👍