Migrate plugin generated from swc plugin new to use .cargo/config.toml instead of .cargo/config to fix warning

[SpanishPear]

Description:
As per https://doc.rust-lang.org/cargo/reference/config.html we should be generating a .cargo/config.toml instead of .cargo/config when creating a new plugin

Motivation - console warnings 😆

BREAKING CHANGE:
Technically this means users must have a toolchain > 1.38 (released september, 2019 - so five years ago).
Given that:

• the public documentation for swc plugins link directly to the latest version of the rust toolchain (currently 1.81)
• 1.38 was > five years ago
• This only impacts new usages of swc plugin new ..
• README.md specifies that the swc-project/swc MSRV is 1.73 anyways - whilst that doesn't specifically refer to generated code, it shows the intent of the project :)

I don't believe it will have material impact.

I will raise a separate PR to generate the correct MSRV for both swc-project/swc and the generated plugin itself.

Related issue (if exists):

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⚠️ No Changeset found

Latest commit: de87966

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[codspeed-hq]

CodSpeed Performance Report

Merging #9740 will not alter performance

_{Comparing SpanishPear:patch-2 (de87966) with main (9f8c14f)}

Summary

✅ 194 untouched benchmarks