[CI] Split the secp256k1 build in parts

Summary:
The build actually runs 3 builds serially, this diffs make them
different configurations so they can run parallel.

Test Plan:

./contrib/teamcity/build-configurations.py build-secp256k1
./contrib/teamcity/build-configurations.py build-secp256k1-endomorphism
./contrib/teamcity/build-configurations.py build-secp256k1-java

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D7398