refactor into groups (#684)

* Refactor tests into "groups", each with its own filter (not/only/requires) to select which providers are appropriate.
* Test driver code is now a lot more simple and clear.
* Add support for not(), only(), and requires() as a way to select/reject providers for a test.
* Add docs explaining how to add tests
* Logging messages are much cleaner now, especially when tests are skipped.
* -start and -end now refer to test groups, not individual tests.  Log messages list the group numbers clearly.
* Add stringer for Capabilities
* Change the order of the tests so that simple tests are first
* Removed knownFailures from providers.json
* fmtjson providers.json

Co-authored-by: Tom Limoncelli <tlimoncelli@stackoverflow.com>

providers/capability_string.go

@@ -0,0 +1,38 @@
+// Code generated by "stringer -type=Capability"; DO NOT EDIT.
+
+package providers
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[CanUseAlias-0]
+	_ = x[CanUseCAA-1]
+	_ = x[CanUsePTR-2]
+	_ = x[CanUseNAPTR-3]
+	_ = x[CanUseSRV-4]
+	_ = x[CanUseSSHFP-5]
+	_ = x[CanUseTLSA-6]
+	_ = x[CanUseTXTMulti-7]
+	_ = x[CanAutoDNSSEC-8]
+	_ = x[CantUseNOPURGE-9]
+	_ = x[DocOfficiallySupported-10]
+	_ = x[DocDualHost-11]
+	_ = x[DocCreateDomains-12]
+	_ = x[CanUseRoute53Alias-13]
+	_ = x[CanGetZones-14]
+	_ = x[CanUseAzureAlias-15]
+}
+
+const _Capability_name = "CanUseAliasCanUseCAACanUsePTRCanUseNAPTRCanUseSRVCanUseSSHFPCanUseTLSACanUseTXTMultiCanAutoDNSSECCantUseNOPURGEDocOfficiallySupportedDocDualHostDocCreateDomainsCanUseRoute53AliasCanGetZonesCanUseAzureAlias"
+
+var _Capability_index = [...]uint8{0, 11, 20, 29, 40, 49, 60, 70, 84, 97, 111, 133, 144, 160, 178, 189, 205}
+
+func (i Capability) String() string {
+	if i >= Capability(len(_Capability_index)-1) {
+		return "Capability(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _Capability_name[_Capability_index[i]:_Capability_index[i+1]]
+}