ci: Upgrade IWYU to 0.27 compatible with Clang 23 #36181

The new IWYU release includes several improvements and bug fixes, including:

• https://github.com/include-what-you-use/include-what-you-use/pull/1991
• https://github.com/include-what-you-use/include-what-you-use/pull/2013
• https://github.com/include-what-you-use/include-what-you-use/pull/2014
• https://github.com/include-what-you-use/include-what-you-use/pull/2058
• https://github.com/include-what-you-use/include-what-you-use/pull/2062
• https://github.com/include-what-you-use/include-what-you-use/pull/2093

This allows us to remove all corresponding workarounds and patches.

Additionally, the compiler intrinsics mapping has switched from a hardcoded file to a dynamically generated one.

Note: This PR is currently a draft because IWYU 0.27 has not yet been officially tagged.

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36181.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #34360 (bench: add WalletBalanceManySpent for high-history wallet scenario by w0xlt)
• #32554 (bench: replace embedded raw block with configurable block generator by l0rinc)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

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🚧 At least one of the CI tasks failed. _{Task lint: https://github.com/bitcoin/bitcoin/actions/runs/34114867585/job/101719212535} _{LLM reason (✨ experimental): CI failed due to a lint-shell (ShellCheck SC2086) error: an unquoted $(clang-<ver> -print-resource-dir) expansion in ci/test/03_test_script.sh triggered Failure generated from lint-shell.py.}

<details><summary>Hints</summary>

Try to run the tests locally, according to the documentation. However, a CI failure may still happen due to a number of reasons, for example:

• Possibly due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

• A sanitizer issue, which can only be found by compiling with the sanitizer and running the affected test.

• An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

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shallow code review ACK 3b944f194fddbcff11f7e5bad4e075a5eac5ed78