Add veneers for panel overrides

[K-Phoen]

Overrides can be quite tedious to define. See:

cog/examples/_go/disk.go

Lines 138 to 177 in fa1fbdc

	// Overrides configuration
	WithOverride(
	dashboard.MatcherConfig{Id: "byName", Options: "Mounted on"},
	[]dashboard.DynamicConfigValue{
	{Id: "custom.width", Value: 260},
	},
	).
	WithOverride(
	dashboard.MatcherConfig{Id: "byName", Options: "Size"},
	[]dashboard.DynamicConfigValue{
	{Id: "custom.width", Value: 93},
	},
	).
	WithOverride(
	dashboard.MatcherConfig{Id: "byName", Options: "Used"},
	[]dashboard.DynamicConfigValue{
	{Id: "custom.width", Value: 72},
	},
	).
	WithOverride(
	dashboard.MatcherConfig{Id: "byName", Options: "Available"},
	[]dashboard.DynamicConfigValue{
	{Id: "custom.width", Value: 88},
	},
	).
	WithOverride(
	dashboard.MatcherConfig{Id: "byName", Options: "Used, %"},
	[]dashboard.DynamicConfigValue{
	{Id: "unit", Value: "percentunit"},
	{Id: "custom.cellOptions", Value: struct {
	Mode string `json:"mode"`
	Type string `json:"type"`
	}{
	Mode: "gradient",
	Type: "gauge",
	}},
	{Id: "min", Value: 0},
	{Id: "max", Value: 1},
	},
	)

They could use some veneers to make them easier to discover and use. The matcher argument seems like a good candidate for pre-built matchers such as dashboard.MatchByName("Size") or dashboard.MatchByRegex("/ io time/")

Defining veneers for the second argument – []DynamicConfigValue – would be great but seems a bit harder.