Merge #10321: Use FastRandomContext for all tests

Merge #10321: Use FastRandomContext for all tests

e94584858 scripted-diff: Use new naming style for insecure_rand* functions (Pieter Wuille)
2fcd9cc86 scripted-diff: Use randbits/bool instead of randrange where possible (Pieter Wuille)
2ada67852 Use randbits instead of ad-hoc emulation in prevector tests (Pieter Wuille)
5f0b04eed Replace rand() & ((1 << N) - 1) with randbits(N) (Pieter Wuille)
3ecabae36 Replace more rand() % NUM by randranges (Pieter Wuille)
efee1db21 scripted-diff: use insecure_rand256/randrange more (Pieter Wuille)
1119927df Add various insecure_rand wrappers for tests (Pieter Wuille)
124d13a58 Merge test_random.h into test_bitcoin.h (Pieter Wuille)
90620d66c scripted-diff: Rename cuckoo tests' local rand context (Pieter Wuille)
37e864eb9 Add FastRandomContext::rand256() and ::randbytes() (Pieter Wuille)

Tree-SHA512: d09705a3ec718ae792f7d66a75401903ba7b9c9d3fc36669d6e3b9242f0194738106be26baefc8a8e3fa6df7c9a35978c71c0c430278a028b331df23a3ea3070