Linkage Monitor GitHub Action to take input of BOM coordinates

Linkage Monitor for java-spanner version 4.0.0 branch is not working. The check is designed to always to choose the latest version in the Libraries BOM.

@benwhitehead 's idea: add new parameter to linkage monitor to provide the bom to validate against `[groupId:artifactId[:version]] `
- if not specified version would default to latest
- if groupId:artifactId are not specified it would default to com.google.cloud:libraries-bom