TS-41699 Migrate maven plugin build to Gradle

[DreierF]

Addresses issue TS-41699

• Changes are tested adequately
• Agent's README.md updated in case of user-visible changes
• CHANGELOG.md updated
• Present new features in N&N
• TGA Tutorial updated
• TIA Tutorial updated

Please respect the vote of the Teamscale bot or flag irrelevant findings as tolerated or false positives. If you feel that the Teamscale config needs adjustment, please state so in a comment and discuss this with your reviewer.

[cqse-teamscale-io]

• agent/src/main/java/com/teamscale/jacoco/agent/PreMain.java:262-276: [Test Gap] Changed method createFallbackLoggerFromConfig has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/PreMain.java:229-259: [Test Gap] Changed method initializeFallbackLogging has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/options/AgentOptionParseException.java:17-19: [Test Gap] Added method AgentOptionParseException has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/options/AgentOptionsParser.java:295-385: [Test Gap] Changed method handleAgentOptions has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/options/AgentOptionsParser.java:492-498: [Test Gap] Added method parsePath has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/options/AgentOptionsParser.java:201-232: [Test Gap] Changed method handleOption has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/options/AgentOptionsParser.java:234-260: [Test Gap] Changed method handleProxyOptions has not been tested. (view in Teamscale)
• agent/src/main/java/com/teamscale/jacoco/agent/upload/teamscale/TeamscaleConfig.java:48-90: [Test Gap] Changed method handleTeamscaleOptions has not been tested. (view in Teamscale)
• report-generator/src/main/java/com/teamscale/jacoco/agent/options/ClasspathUtils.java:31-45: [Test Gap] Changed method resolveClassPathEntries has not been tested. (view in Teamscale)
• report-generator/src/main/java/com/teamscale/jacoco/agent/options/FilePatternResolver.java:179-195: [Test Gap] Changed method getSinglePath has not been tested. (view in Teamscale)

See other 4 changed untested methods.