add support for choosing congestion control alg

[qzhuyan]

• new conn opt: congestion_control_algorithm

• try fix flaky test is casued by handshake failure, suspect it relates to async settings of disable_1rtt_encryption
  {conn_handshake_fail,1},
  {conn_protocol_errors,2},
  {conn_no_alpn,1},
  {pkts_suspected_lost,1},
  {pkts_dropped,2},
  {pkts_decryption_fail,1},

[coveralls]

Pull Request Test Coverage Report for Build 11213823812

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 13 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.3%) to 86.291%

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Files with Coverage Reduction	New Missed Lines	%
c_src/quicer_nif.c	1	81.03%
c_src/quicer_config.c	12	86.79%

Totals
Change from base Build 11181420457:	-0.3%
Covered Lines:	3909
Relevant Lines:	4530

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💛 - Coveralls