Add fuzzer version of randomized prevector test
Summary:
The current prevector test effectively randomly generates a number of operations to perform on a prevector and a normal vector, and checks consistency between the two. By converting this into a fuzzer the operations can be targetted rather than random.
Backport of core PR18529.
Test Plan:
ninja bitcoin-fuzzers ./src/test/fuzz/prevector <path_to_corpus>
Reviewers: #bitcoin_abc, majcosta
Reviewed By: #bitcoin_abc, majcosta
Differential Revision: https://reviews.bitcoinabc.org/D9003