test: Update fuzz tests to use the built-in infrastructure

Go 1.18 supports fuzzing natively, so this patch migrates our fuzzing
tests to make use of it.

internal/aliases/testdata/fuzz/FuzzReader/1c24d2215db69748c6fd16797673ad11ebc7e6167fe1bc1f54c6959ec10407b6

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("# First some valid cases.\na: b\nc: d@e, f,\nx: | command\n\n# The following is invalid, should be ignored.\na@dom: x@dom\n\n# Overrides.\no1: a\no1: b\n\n# Finally one to make the file NOT end in \\n:\ny: z\n")

internal/aliases/testdata/fuzz/FuzzReader/4adaceaa32e2b32c00322948769d62c2dd42e1d9f4950d3c5b411c710e6d4a86

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\nfail: | false\n\n")

internal/aliases/testdata/fuzz/FuzzReader/8234d8c5719f30e50525290db70743bf97d940e60591cf4a638c72158d35504a

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\naliasA: aliasB@srv-B\n")

internal/aliases/testdata/fuzz/FuzzReader/c9c80ba9f513841cb081fe9bb7439d36f9f7a06bb999d4c39441991ccc878a9e

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\n# Easy aliases.\npepe: jose\njoan: juan\n\n# UTF-8 aliases.\npitanga: ñangapirí\nañil: azul, índigo\n\n# Pipe aliases.\ntubo: | writemailto ../.data/pipe_alias_worked\n\n")

internal/aliases/testdata/fuzz/FuzzReader/d40a98862ed393eb712e47a91bcef18e6f24cf368bb4bd248c7a7101ef8e178d

@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("")

internal/aliases/testdata/fuzz/corpus/t-002

@@ -1,14 +0,0 @@
-# First some valid cases.
-a: b
-c: d@e, f,
-x: | command
-
-# The following is invalid, should be ignored.
-a@dom: x@dom
-
-# Overrides.
-o1: a
-o1: b
-
-# Finally one to make the file NOT end in \n:
-y: z

internal/aliases/testdata/fuzz/corpus/t-003

@@ -1,12 +0,0 @@
-
-# Easy aliases.
-pepe: jose
-joan: juan
-
-# UTF-8 aliases.
-pitanga: ñangapirí
-añil: azul, índigo
-
-# Pipe aliases.
-tubo: | writemailto ../.data/pipe_alias_worked
-

internal/aliases/testdata/fuzz/corpus/t-004

@@ -1,3 +0,0 @@
-
-fail: | false
-

internal/aliases/testdata/fuzz/corpus/t-005

@@ -1,2 +0,0 @@
-
-aliasA: aliasB@srv-B