Switch snapshot ci to new app and rework notification design

[rolnico]

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?
Feature

What is the current behavior?
CI uses some action to format slack notification

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

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

• Yes
• No

If yes, please check if the following requirements are fulfilled

• The Breaking Change or Deprecated label has been added
• The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

Existing integration branches for the current snapshot version of powsybl-core should be renamed by adding the prefix integration/powsybl-core-. (For instance, 6.7.0-SNAPSHOT => integration/powsybl-core-6.7.0-SNAPSHOT).

Other information:

⚠️ Important note: Before this PR, the integration branches used for each repo were called with the snapshot version of powsybl-core (for instance 6.6.0-SNAPSHOT). Now their name should be prefixed with integration/powsyblcore-. In our previous example, the branches must be called integration/powsyblcore-6.6.0-SNAPSHOT.
As a consequence, only maintainers can create these branches or force-push into them (see the branching strategy documentation).

[olperr1]

Once merged, powsybl/powsybl-dev-tools#120 should be adapted to reflect the integration branch naming pattern change.

[olperr1]

The workflow previously worked with the default v4 version (so v4.2.2).
Did something prevents to use this version?

[rolnico]

Nope, I just put the same version we use on some other repos but we surely can update it

[olperr1]

Same with this action:
The workflow previously worked with the default v4 version (so v4.6.0).
Did something prevents to use this version?

[rolnico]

same answer

[sonarqubecloud]

Quality Gate passed for 'pypowsybl-parent'

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 SonarQube Cloud

[sonarqubecloud]

Quality Gate passed for 'pypowsybl'

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 SonarQube Cloud