Change the following functions on OpObserver to take in DatabaseName rather than a string for dbName:

• onDropDatabase
• onApplyOps

Set the "tid" field in the oplog entry for each of the follow commands using the tenantId on the NamespaceString or DatabaseName object passed in (i.e. OpObserverImpl::onStartIndexBuild).

• onCreateIndex
• onStartIndexBuild
• onCommitIndexBuild
• onAbortIndexBuild
• onInternalOpMessage
• onCollMod
• onDropCollection
• onDropIndex
• onEmptyCapped
• onImportCollection
• preRenameCollection
• postRenameCollection
• onRenameCollection
• onDropDatabase
• onApplyOps

Be sure not to include the tenantID in the "ns" field in any oplog entries (i.e. like here in onCreateIndex). There are some commands that log namespaces in fields other than "ns" as well, be sure not to include the tenantID in these either:
Special cases:

• onDropCollection
  • Don't include the tenantID in the collection name logged in the "o" field
• preRenameCollection
  • Don't include the tenantID in the from and to namespaces

We can again add tests to OpObserverTest, though we probably don't need to add a test case for every command.