Added borrowed value conversion traits for geo_types.

[metasim]

• [X] I agree to follow the project's code of conduct.

• [X] I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

Reworked current implementation to use borrowed values, and created macro to generate owned value variants that delegate to the borrowed value ones.

Note: Until #201 is addressed, invalid geometry conversions will be cloned during error reporting.

[michaelkirk]

bors r=michaelkirk,urschrei

[bors[bot]]

Build succeeded:

• build_and_test