[composer][5/5]Implement default unary rpc method's sample code#515

summer-ji-eng wants to merge 19 commits intorpc_unary_paged_sc_33googleapis/sdk-platform-java:rpc_unary_paged_sc_33from

rpc_unary_default_sc34googleapis/sdk-platform-java:rpc_unary_default_sc34Copy head branch name to clipboard