Update pest 2.4.0 => 2.7.4

[dmitrii-ubskii]

What is the goal of this PR?

We update to pest and pest-derive v2.7.4, which among other things purports to fix the error where deriving Parser fails on "undeclared crate or module alloc" (pest-parser/pest#900).

What are the changes implemented in this PR?

We also clean up some compile warnings (unused imports and hashes).

[typedb-bot]

PR Review Checklist

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Trivial Change

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

Code

• Packages, classes, and methods have a single domain of responsibility.
• Packages, classes, and methods are grouped into cohesive and consistent domain model.
• The code is canonical and the minimum required to achieve the goal.
• Modules, libraries, and APIs are easy to use, robust (foolproof and not errorprone), and tested.
• Logic and naming has clear narrative that communicates the accurate intent and responsibility of each module (e.g. method, class, etc.).
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Architecture

• Any required refactoring is completed, and the architecture does not introduce technical debt incidentally.
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• The architecture intuitively reflects the application domain, and is easy to understand.
• The architecture has a well-defined hierarchy of encapsulated components.
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