tree-optimization/111489 - turn uninit limits to params

tree-optimization/111489 - turn uninit limits to params

The following turns MAX_NUM_CHAINS and MAX_CHAIN_LEN to params which
allows to experiment with raising them.  For the testcase in PR111489
raising MAX_CHAIN_LEN from 5 to 8 avoids the bogus diagnostics
at -O2, at -O3 we need a MAX_CHAIN_LEN of 6.

	PR tree-optimization/111489
	* doc/invoke.texi (--param uninit-max-chain-len): Document.
	(--param uninit-max-num-chains): Likewise.
	* params.opt (-param=uninit-max-chain-len=): New.
	(-param=uninit-max-num-chains=): Likewise.
	* gimple-predicate-analysis.cc (MAX_NUM_CHAINS): Define to
	param_uninit_max_num_chains.
	(MAX_CHAIN_LEN): Define to param_uninit_max_chain_len.
	(uninit_analysis::init_use_preds): Avoid VLA.
	(uninit_analysis::init_from_phi_def): Likewise.
	(compute_control_dep_chain): Avoid using MAX_CHAIN_LEN in
	template parameter.