New datastructure for iet

[videlec]

It was decided to develop flatsurf as an independent package

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Old description

In #8386 we decided to only move iet to sage/dynamics. This ticket stands for the creation of the new datatype and the correction of the following bug

sage: p = iet.Permutation('a b','b a')
sage: q = iet.Permutation('b a','a b')
sage: p == q
True

CC: @sagetrac-Fougeroc

Component: combinatorics

Keywords: iet, flat surfaces

Reviewer: Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/14683

[videlec]

Commit: 530fe85

[videlec]

Branch: u/vdelecroix/14683-iet_new_datastructure

[videlec]

New commits:

530fe85

Initial commit: new datastructure for iet.

[videlec]

Changed keywords from none to iet, flat surfaces