Add build to .gitignore in sui move new

[mdgeorge4153]

Description

• Adds build/* to .gitignore when invoking sui move new (extending it if it already exists)
• Splits out move new implementation into smaller functions

Test plan

I added to the move new unit tests; checking the case where the .gitignore already exists, and extended the existing tests to check that it was added.

Note that I didn't add tests to sui move new, only move new.

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Release notes

Check each box that your changes affect. If none of the boxes relate to your changes, release notes aren't required.

For each box you select, include information after the relevant heading that describes the impact of your changes that a user might notice and any actions they must take to implement updates.

• Protocol:
• Nodes (Validators and Full nodes):
• Indexer:
• JSON-RPC:
• GraphQL:
• CLI: When issuing sui move new command, a .gitignore file will be added to the project's folder.
• Rust SDK:
• REST API:

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Name	Status	Preview	Comments	Updated (UTC)
sui-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 26, 2024 5:56pm

3 Skipped Deployments

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[stefan-mysten]

Thanks @mdgeorge4153 for starting the work on this. Left a few comments and looking forward to see this merged!

Regarding the Release notes part from above, when a box is selected, we need to enter a description with the change. For example, in this case it could be something like this:

Check each box that your changes affect. If none of the boxes relate to your changes, release notes aren't required._

For each box you select, include information after the relevant heading that describes the impact of your changes that a user might notice and any actions they must take to implement updates.

Protocol:
- [ ] Nodes (Validators and Full nodes):
- [ ] omitted the rest of options
- [x] CLI: When issuing `sui move new` command, a `.gitignore` file will be added to the project's folder.

[amnn]

Looks great modulo some smaller comments, thanks for the surrounding clean-ups @mdgeorge4153 !

[stefan-mysten]

LGTM!