fix: Update to JDK21 - EXO-71474 - Meeds-io/MIPs#91

[rdenarie]

Remove usage of SecurityManager as it is deprecated for removal in jdk21 Remove also usage of classes

• SecurityHelper
• PrivilegedSystemHelper
• PrivilegedFileHelper
• SecureList
• SecureSet
• SecureCollections

These classes are here only to use securityManager, and as it is removed, it is no more necessary

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud