Update examples

[tomas-langer]

Update examples:

MP:

• only use META-INF/microprofile-config.properties and application.yaml on the classpath for MP
• Remove setup of logging.properties, done automatically now - PR Logging setup in examples and templates #2583
• Remove Main classes unless they do something important (and use io.helidon.microprofile.cdi.Main as the main class)
• Remove application classes unless they are significant (e.g. add @ApplicationPath that diffes from /)
• Use ${key} instead of '{ALIAS=key} in all examples - PR Using config reference instead of ${ALIAS= #2579

SE:

• Use Helidon WebClient for tests and examples

[barchetta]

Some of this addressed by PR #1715