Add feature flags for selecting rustls or openssl as the tls implementation.

[AlterionX]

A simple switch for allowing reqwest to compile with rustls instead of native which relies on openssl.

openssl is known to be a non-trivial dependency in the compilation process.

[AlterionX]

I may need some instructions about how to test the change.

Running cargo test seems to fail by default, even on the current master.

[ivnsch]

Thanks for you contribution! To understand better/for the record: why do we want to keep the possibility to use native? From a quick search it seems to be possibly quicker updates via the OS libraries and smaller binaries (dynamic linking), is this correct?

[ivnsch]

I may need some instructions about how to test the change.

Running cargo test seems to fail by default, even on the current master.

The tests are WIP (#1, #62). Those failing tests are integration tests that depend on a running local network and indexer. The CI currently executes this (which excludes them):

cargo test --workspace --lib --examples --test test_account --test test_logic_signature

[AlterionX]

Oops, I've been a bit busy with work and forgot to check back on this.

About retaining the ability to use native: yes, that's basically it. The actual implementation should be abstracted away cleanly by lower level libs anyways, and not be a maintenance burden.