Issue 4740 - JPA integration tests should run on every build

[Tomas-Kraus]

Added profiles to automatically trigger test setup with in memory H2 database.
JPA tests module added to integration tests.

@romain-grecourt This is an attpempt to run JPA integradion tests with default profile triggered as <activeByDefault>true</activeByDefault> when no other DB profile is selected.
This is done in JPA integration tests parent POM.

1. This h2 profile sets DB properties and stores them in file.
2. Existence of this file triggers h2 profile in appl module so default test setup is started just from helidon's root 'mvn clean install -Ptests'. It requires no docker.

[romain-grecourt]

Looks like none of the updated tests are running:

jakarta.ws.rs.ProcessingException: java.net.ConnectException: Connection refused
	at io.helidon.tests.integration.jpa.appl.test.InsertIT.testInsertTownWithStadium(InsertIT.java:53)
Caused by: java.net.ConnectException: Connection refused
	at io.helidon.tests.integration.jpa.appl.test.InsertIT.testInsertTownWithStadium(InsertIT.java:53)

[Tomas-Kraus]

It was running well on my local environment. Anyway, this must be fixed.

[Tomas-Kraus]

@romain-grecourt This is funny. I tested it on my machine with maven 3.8.6 again and it works!. Looks like maven devs chganged profiles initialization in latest version somehow.
Anyway, this means that we can't rely on this pattern. I changed it to the most stupid simple selection:

        <profile>
            <id>h2</id>
            <activation>
                <property>
                    <name>!db</name>
                </property>
            </activation>
...
        <profile>
            <id>mysql</id>
            <activation>
                <property>
                    <name>db</name>
                    <value>mysql</value>
                </property>
            </activation>
...
        <profile>
            <id>pgsql</id>
            <activation>
                <property>
                    <name>db</name>
                    <value>pgsql</value>
                </property>
            </activation>

Property db allows to switch databases.

I'll modify DbClient tests to follow the same patrtern and will add it to tests run too after this is merged.