Spanner: migrate all unary call methods to gapic and inject headers - #3112

Spanner: migrate all unary call methods to gapic and inject headers#3112

yihanzhen merged 5 commits into

googleapis:spanner-gapic-migrationgoogleapis/google-cloud-java:spanner-gapic-migrationfrom

yihanzhen:spanner-inject-metadatayihanzhen/google-cloud-java:spanner-inject-metadataCopy head branch name to clipboard