Add parallelization option

[lenianiva]

When we figure out how cvc5 behaves when called from multiple threads (cvc5/cvc5#12558) we can add a conditional flag to build it with parallelization support.

Some questions:

1. Is it safe to have Sync on TermManager?
2. Is it safe to have Sync on Term?
3. Can TermManager call primitives with no locks?