feat: define Asymptotics.IsSubpolynomial

[m13683320924-hue]

This PR defines Asymptotics.IsSubpolynomial l f g, meaning that f is asymptotically bounded by 1 + ‖g‖ ^ k for some k : ℕ.

It also adds basic closure lemmas for constants, addition, multiplication, and natural powers.

Towards #32658.

The formalization was developed with the help of Doubao-Seed-2.0-code and manually checked in Lean.

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[github-actions]

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[github-actions]

PR summary 13338c3c40

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Analysis.Asymptotics.Subpolynomial (new file)	1472

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Declarations diff

+ IsSubpolynomial
+ IsSubpolynomial.add
+ IsSubpolynomial.const
+ IsSubpolynomial.def
+ IsSubpolynomial.mul
+ IsSubpolynomial.pow
+ isSubpolynomial_iff
+ one_plus_pow_le_two_mul_one_plus_pow
+ product_one_plus_pow_le_four_mul_one_plus_pow_sum

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

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No changes to strong technical debt.

No changes to weak technical debt.

[github-actions]

✅ PR Title Formatted Correctly

The title of this PR has been updated to match our commit style conventions.
Thank you!