Upgrade boost dependency in superbuild

boost 1.60.0 is 4 years old now, it'd be nice to upgrade it to something more recent. As of today, the current version is v1.70.0

Is there any specific bugfix or feature that you think would benefit OTB in versions > 1.60? If not we can still upgrade, but it will be low priority.

In an OTB subproject, I wanted to use boost.hana. As OTB was already compiled and installed with a dependency to boost 1.60.0, hana isn't directly available to me. It would imply that my clients and I reinstall OTB manually, which is too much trouble.

Necessary for #1564. But we need to go for boost >= 1.69 (see #1871 (closed)).

also TODO: update boost min version in doc: https://gitlab.orfeo-toolbox.org/orfeotoolbox/otb/blob/develop/Documentation/Cookbook/rst/CompilingOTBFromSource.rst

But do we have a minimum version for boost?
EDIT: 1.35 for OTB, 1.48 for shark

At some point I wanted to replace various dynamic allocations of small sizes with boost::container::small_vector, but that's only available since 1.58.

mentioned in issue #1871 (closed)

added refactoring label

added ~08pt label

added CNES backlog label

mentioned in merge request !554 (merged)

Boost version is now 1.69, see !5540.

closed