Convert more goconvey tests to normal go tests

[lukedirtwalker]

Also introduce xtest.AssertErrorsIs and use it instead of manual asserts with xerrors.Is

Contributes #3016

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This change is 

[oncilla]

Reviewed 48 of 48 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @lukedirtwalker)

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go/lib/l4/udp_test.go, line 33 at r1 (raw file):

func TestUDPFromRaw(t *testing.T) {
	t.Run("Content must match", func(t *testing.T) {

drop all t.Run here

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go/lib/scrypto/asym_test.go, line 63 at r1 (raw file):

func TestGenKeyPairs(t *testing.T) {
	t.Run("GenKeyPairs should return a valid Curve25519xSalsa20Poly1305 key pair",

Table driven test would be nice here.

But I understand it is a bit tedious, so feel free to add or not.

[lukedirtwalker]

Reviewable status: 47 of 48 files reviewed, 1 unresolved discussion (waiting on @oncilla)

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go/lib/l4/udp_test.go, line 33 at r1 (raw file):

Previously, Oncilla wrote…

drop all t.Run here

Done.

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go/lib/scrypto/asym_test.go, line 63 at r1 (raw file):

Previously, Oncilla wrote…

Table driven test would be nice here.

But I understand it is a bit tedious, so feel free to add or not.

Not this time, I tried to it for Decrypt, but it was more lines so I aborted the mission.

[oncilla]

Reviewed 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved