Fix node breaker disconnect

[flo-dup]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem?

No

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

• Disconnect may open non-related breakers
• Disconnect may return true when not disconnected
• Map node to aggregate node is duplicated

What is the new behavior (if this is a feature change)?

• Disconnect does not open non-related breakers
• Disconnect does return true only if disconnect successful
• Reusing the node to aggregate node map of ConnectivityInspector

Does this PR introduce a breaking change or deprecate an API?

No

[flo-dup]

          L                        LA
          |                         |
       ---1---                      4
       |     |                      |
      BR1   BR2                    BR4
       |     |                      |
       ---0---   -----BR3-----   ---3---
        BBS1                      BBS2

When disconnecting load L, the minimal cut is looked for all the bbs, including BBS2. The minimal cut for L - BBS2 is BR3, hence BR3 is opened when disconnecting L, whereas it is not needed.

[flo-dup]

    L1                   L2
     |                    |
     1                    3
     |                    |
    D1                   D2
     |                    |
  ---0---  ----BR----  ---2---
    BBS1                BBS2

Similar case, with a load which cannot be disconnected because of disconnector D1. But disconnecting terminal of load L1 returns true, as BR is opened. Nonetheless it should return false and BR should remain open.

[flo-dup]

Other unit test which fails when disconnecting load. Switch BR1 is opened, load remains linked with line and 2wt.

     Load        Line    2WT
       |          |       |
   ----2---       3       4
   |      |       |       |
  BR2    BR3     BR4     BR5
   |      |       |       |
   -----------1------------
              |
             BR1
              |
   -----------0------------
            BBS1

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

96.0% Coverage
0.0% Duplication