Store cursor position when changing lines

[jamesreprise]

What is the goal of this PR?

We store cursor positions when changing lines as described in https://github.com/vaticle/typedb-studio/issues/748. This is standard behaviour in other IDEs, such as IntelliJ IDEA and VSCode.

Before:

https://github.com/vaticle/typedb-studio/assets/51956016/9a4232b2-fb41-4276-9b48-76d741143329

After:

https://github.com/vaticle/typedb-studio/assets/51956016/0f311437-15f4-4a66-96d8-0005dedc6ad7

What are the changes implemented in this PR?

We store an additional piece of data in Cursor, lastCol. This remembers the last position of the column, which we only forget upon the creation of a new cursor by a method other than moving up or down a line.

Additional info

Closes https://github.com/vaticle/typedb-studio/issues/748

[typedb-bot]

PR Review Checklist

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Trivial Change

• [x] This change is trivial and does not require a code or architecture review.

Code

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Architecture

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