chore: forc-index-build preserve yaml comments

[ra0x3]

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Description

• PR makes it such that comments will remain in your manifest after forc index build
• serde_yaml obviously does not (and will not) handle comments
• The idea in this PR is to just add a small manifest proxy RawManifest to cache comments on read, and write the comments back on write
• This was actually not easy 😅

Testing steps

• Build plugin binary locally cargo build -p forc-index --release
• Create a new project using local binary /path/to/fuel-indexer/target/release/forc-index new fool --namespace fuel
• Build it /path/to/fuel-indexer/target/release/forc-index build
• You should notice that the comments remain in the same place after forc index build

Changelog

• chore: forc-index-build preserve yaml comments

[lostman]

Why add an empty line here? Is this something the comment-preserving code is forcing us to do?

[ra0x3]

@lostman

• Well the alternative to simply joining each line in the manifest on a newline, is - finding the particular lines that (we think) shouldn't have new lines above them (e.g., wasm: ~) and removing the newline in-between this line and its precursor line
  • Nothing forcing us to not do this, I just thought it was a little much for something small/subjective

[lostman]

I see. I think that's fine. What I expected is that nested items would not be separated by empty lines:

toplevel:
  nested: 123

another-top-level:
  another-nested: 123

[ra0x3]

@lostman Let me push up a change