[327] Rudimentary thinning

[voj]

Implements #327

A set of thinning strategies for subduction and crustal ruptures that reduce the number of potential Hikurangi joint ruptures from 2.6E10 to 110409.

The thinning criteria in this PR will be good for enough for early development of joint rupture creation but will need to be improved.

Subduction filtering:

• size increase needs to be at least 10%
• ruptures of the same size avoid overlapping

Crustal ruptures:

• max cumulative azimuth change 10
• max cumulative rake change 10

[voj]

• move into experimental namespace

[voj]

moved to new namespace and created new PR that combines this and https://github.com/GNS-Science/nzshm-opensha/pull/328