Improve C3T3 IO

[maxGimeno]

Summary of Changes

Save/load edges in complex in c3t3 operator<</>>

Release Management

• Affected package(s):Mesh_3
• Issue(s) solved (if any): fix Mesh_3: Save/load c3t3 objects correctly #2359

TODO

• Wait for Triangulation_23: Add functions for extra data in IO #5145 and then rework Edit: the implementation actually cannot rely on Triangulation_23: Add functions for extra data in IO #5145

[sloriot]

@lrineau should this PR be closed?

[lrineau]

@lrineau should this PR be closed?

No. Now that we have abandoned #5145, this PR seems the right thing to do.

[janetournois]

@sloriot is this what you meant?
The assertion added in commit f11cc0f fails
I am checking why

[janetournois]

It fails because c3t3 (to be written) is output with its complex edges, so this is added to the end of the dump :

2
1 3 5
1 4 6

though c3t3_2 (loaded from the dump of c3t3) does not have complex edges, they have not been loaded.

[sloriot]

#7821 mentioned that it is similar. Shall we close this PR? @ange-clement @janetournois

[janetournois]

they are similar and follow the same target, but for now they are complementary and should be "merged" (if I'm right, #7821 does not contain the "write" code for now)