[Java][resttemplate] Add test for bearer auth

[kota65535]

This PR is a preliminary step to fix #16059.
Currently, the feature is added only for RestTemplate library. Before adding the feature for other libraries as well, I would like to add tests of that.

• Added API to test HTTP bearer auth for sample Echo API
• Added sample of Echo API with Java RestTemplate library
• Added test for HTTP bearer auth

To Java technical committee: @bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @martin-mfg (2023/08)

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