feat(Analysis/Calculus/Deriv): add deriv_const_mul_id'

[emlis42]

This PR adds a simp lemma for the derivative of multiplication by a constant on the left.

In practice, simp is already able to simplify fun x => x * c and fun x => x / c. However, it getting stuck on fun x => c * x and deriv (HMul.hMul c).

This PR fix this by adding a simp lemma so that simp can also handle fun x => c * x without requiring an explicit rw [deriv_const_mul].

This is useful for examples such as:

example {t : ℝ} (ht : t ≠ 0) : deriv (fun x => x ^ 2 / (2 * x)) t = 1 / 2 := by
  simp (disch := first | fun_prop (disch := grind) | grind); field

example {t : ℝ} : deriv (HMul.hMul 2) t = 2 := by
  simp

[github-actions]

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[github-actions]

PR summary 96c2df6e3d

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff

+ deriv_const_mul_id
+ deriv_const_mul_id'

You can run this locally as follows

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

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

The doc-module for scripts/pr_summary/declarations_diff.sh contains some details about this script.

---

No changes to technical debt.

You can run this locally as

./scripts/reporting/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[emlis42]

!bench

[leanprover-radar]

Benchmark results for c7edc0d against 96c2df6 are in. No significant results found. @emlis42

• ✅ build//instructions: -805.3M (-0.00%)

Small changes (1🟥)

• 🟥 build/module/Mathlib.Tactic.FunProp.ToBatteries//instructions: +544.5M (+7.87%)