fix(cli): resolve cfg directive warnings in default project templates (#3740)

[hasip-timurtas]

Fixes #3740

This pull request refines the Rust template for Solana programs in cli/src/rust_template.rs. Key updates include removing outdated configurations, adding new debugging and customization options, and introducing linting rules for better code quality.

Removal of outdated configurations:

• Removed references to Xargo.toml as it is no longer needed for modern Solana builds using SBF. ([cli/src/rust_template.rsL40-R40](https://github.com/solana-foundation/anchor/pull/3748/files#diff-caba398fa4ca1762b150abb98bffb6a49bb4398c43e900e588511209a88aa453L40-R40))
• Eliminated the xargo_toml function and its associated configuration for BPF targets, as it is now obsolete. ([cli/src/rust_template.rsL221-L226](https://github.com/solana-foundation/anchor/pull/3748/files#diff-caba398fa4ca1762b150abb98bffb6a49bb4398c43e900e588511209a88aa453L221-L226))

Addition of debugging and customization options:

• Added new features: anchor-debug, custom-heap, and custom-panic to enhance debugging and allow custom memory and error-handling configurations. ([cli/src/rust_template.rsR207-R217](https://github.com/solana-foundation/anchor/pull/3748/files#diff-caba398fa4ca1762b150abb98bffb6a49bb4398c43e900e588511209a88aa453R207-R217))

Code quality improvements:

• Introduced linting rules under [lints.rust] to warn about unexpected configurations, specifically targeting cfg(target_os, values("solana")). ([cli/src/rust_template.rsR207-R217](https://github.com/solana-foundation/anchor/pull/3748/files#diff-caba398fa4ca1762b150abb98bffb6a49bb4398c43e900e588511209a88aa453R207-R217))

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[Aursen]

Great one @jacobcreech

[jacobcreech]

Thank you for the contribution!

[hasip-timurtas]

Thank you @Aursen @jacobcreech!

Regarding the CI failures, they are from existing Clippy warnings and formatting issues in master, not related to the rust_template.rs changes in this PR.

To keep this PR focused, I've opened #3751 to address all the CI blockers separately:

• Fixed clippy warnings (obfuscated-if-else, result-large-err, io-other-error)
• Fixed TypeScript formatting in test files

Once #3751 is merged, this PR should pass all checks without any modifications needed.