feat: QUIC Client Initial parser

[kelmenhorst]

This diff is a draft for adding a routine to parse QUIC Client Initial packets.
This is useful for netem because it will allow us to emulate middleboxes that read and filter based on the SNI and protected QUIC header fields.

Reference issue: #2480

[coveralls]

Pull Request Test Coverage Report for Build 5471902144

• 188 of 273 (68.86%) changed or added relevant lines in 3 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-1.2%) to 80.898%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dissect.go	1	3	33.33%
quiccrypto.go	49	64	76.56%
quicparse.go	138	206	66.99%

Files with Coverage Reduction	New Missed Lines	%
linkfwdfull.go	2	97.84%
router.go	2	79.46%

Totals
Change from base Build 5446630722:	-1.2%
Covered Lines:	2287
Relevant Lines:	2827

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💛 - Coveralls