[DOC-10501] Update Transactions.adoc and Create Dedicated Transactions Walkthrough

[sarahlwelton]

I noticed an issue with our multiple transactions.adoc files when I was doing some updates for page tag types.

The purpose of this PR is to add some consistency in what content exists under which page type, and provide a better overview to users of how to use transactions in Couchbase.

There were a lot of pages that this PR touches because of the nature of the transactions documentation, and the larger content pages needed a lot of updating.

[simon-dew]

Thanks for this @sarahlwelton ! I'll be able take a look at this PR after the end of October, if no-one else looks at it first.

[ggray-cb]

@simon-dew, @sarahlwelton, is this PR still of value?

[simon-dew]

Thanks @ggray-cb . I think the ideas and changes in this PR have been implemented by more recent PRs in later versions. Closing this one.