Tail expectation formula for L1 random variable

[Yosuke-Ito-345]

Motivation for this change

Add the tail expectation formula expectation_cdf_ccdf for any L1 random variable.
This is a combined version of lemmas ge0_expectation_ccdf and le0_expectation_cdf.

Checklist

• added corresponding entries in CHANGELOG_UNRELEASED.md

• added corresponding documentation in the headers

Reference: How to document

Merge policy

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• PRs with several commits that make sense individually and that
  all compile are preferentially merged into master.
• PRs with disorganized commits are very likely to be squash-rebased.

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[Yosuke-Ito-345]

@affeldt-aist @t6s
I’m not sure what caused this error. Is there anything I should do on my side?

[affeldt-aist]

Here is the error message:

File "./reals/signed.v", line 6, characters 29-37:
Error: Cannot find a physical path bound to logical path
unstable with prefix mathcomp.

and here is the problematic code:

From HB Require Import structures.
From mathcomp Require Import ssreflect ssrfun ssrbool.
From mathcomp Require Import ssrnat eqtype choice order ssralg ssrnum ssrint.
#[warning="-warn-library-file-internal-analysis"]
From mathcomp Require Import unstable.
From mathcomp Require Import mathcomp_extra.

I don't understand why it fails suddenly (maybe @proux01 knows)
but do not worry: signed.v is a deprecated file, I will test on my side ASAP,
worst case scenario: we don't find a fix, then we might simply give up on Coq 8.20.

[Yosuke-Ito-345]

@affeldt-aist
Thank you for investigating this error. I really appreciate your help.