update syntax for labels

[miller-time]

where before the filter syntax would've been hq read '.block["label"]' now it's hq read '.block{"label"}'

this allows us to treat .name and ["name"] equivalently, with the added bonus that quoting the value allows you to use characters that aren't valid identifier characters.

here's an example:

another_block "some_label" {
    m = {
        "map@key1": "map@value1",
        "map@key2": "map@value2",
    }
}

another_block "another_label" {
    m = {
        "map@key1": "map@value3",
        "map@key2": "map@value4",
    }
}

$ hq read -f example.hcl '.another_block{"some_label"}.m["map@key1"]'
"map@value1"

$ hq read -f example.hcl '.another_block{"some_label"}.m["map@key2"]'
"map@value2"