Bump MSRV to 1.88.0

[ysaito1001]

Motivation and Context

Bumps MSRV to 1.88.0

Description

Although the number of files changed is large, the changes themselves are straightforward. During MSRV upgrade to 1.88.0, one of the clippy warnings enforced is clippy::uninlined_format_args, i.e. suggesting to update

format!("{}", a);

to

format!("{a}");

The PR swept through the codebase and updated almost all the occurrences, except for:

• codegen-client (suppressed the following)
  • RequestBindingGenerator
  • ‎EndpointTraitBindingGenerator
• codegen-server
  • Fix uninlined_format_args in server codegen #4366

Testing

• CI

Checklist

• For changes to the smithy-rs codegen or runtime crates, I have created a changelog entry Markdown file in the .changelog directory, specifying "client," "server," or both in the applies_to key.
• For changes to the AWS SDK, generated SDK code, or SDK runtime crates, I have created a changelog entry Markdown file in the .changelog directory, specifying "aws-sdk-rust" in the applies_to key.

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• AWS SDK (ignoring whitespace)
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• AWS SDK (ignoring whitespace)
• Client Test (ignoring whitespace)
• Server Test (ignoring whitespace)
• Server Test Python (ignoring whitespace)
• Server Test Typescript (ignoring whitespace)

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