feat: execute Hilla tasks whenever Hilla is available

[tepi]

Execute Hilla tasks (TaskGenerateOpenAPI and TaskGenerateEndpoint) whenever Hilla is available on the classpath. These tasks should determine the required actions themselves, instead of Flow trying to do it.

Fixes #20289
Fixes #18800

[github-actions]

Test Results

1 165 files  + 46  1 165 suites  +46   1h 32m 16s ⏱️ -5s
7 623 tests +340  7 567 ✅ +341  56 💤 ±0  0 ❌ ±0 
7 975 runs  +394  7 910 ✅ +393  65 💤 +2  0 ❌ ±0 

Results for commit ce90444. ± Comparison against base commit 248bbd3.

♻️ This comment has been updated with latest results.

[tepi]

For reviewers to test this:

1. You need local clones of flow, hilla and platform repos
2. For Flow checkout this branch, for Hilla checkout this branch, for Platform checkout main branch
3. Build flow: mvn clean install -DskipTests
4. Build hilla: npm run build , then mvn clean install -DskipTests
5. Build vaadin maven plugin: mvn clean install -DskipTests in platform/vaadin-maven-plugin
6. After that test with a project from start, using 24.6-SNAPSHOT as the vaadin version

[tepi]

@mshabarov When you have time could you check that it still works for your use case with the latest change?

[mshabarov]

Test manually with the following scenarios:

1. Vaadin app has only Java views and a ReactAdapter
2. Vaadin app has only TS view
3. Vaadin app has a TS view and a ReactAdapter.

Works as expected. LGTM.

[mshabarov]

⚠️ Let's not merge this until we get a green light from Hilla team for vaadin/hilla#2938.

I'll change this PR as per vaadin/hilla#2938 (comment)

[sonarqubecloud]

Quality Gate passed

Issues
1439 New issues
9 Accepted issues

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

See analysis details on SonarQube Cloud