feat: Add key/value pair QoL improvements

[Techassi]

This PR adds two QoL improvements to the key/value pair API:

• Add TryFrom<[(K, V); N]> impl for labels and annotations
• Add Labels::parse_insert() and Annotations::parse_insert() functions. They take impl TryInto<_> as a parameter.

[NickLarsenNZ]

Just so I understand it correctly, does that mean instead of:

    let labels: Labels =
        BTreeMap::from([("k", "v")])
            .try_into()
            .context(BuildLabelSnafu)?;

I would now do:

    let labels = Labels::try_from([("k", "v")])
            .context(BuildLabelSnafu)?;

---

Edit: I see the test that basically shows my second version

[Techassi]

Yes! See

operator-rs/src/kvp/mod.rs

Lines 335 to 343 in 1c444b6

	fn labels_from_array() {
	let labels = Labels::try_from([
	("stackable.tech/managed-by", "stackablectl"),
	("stackable.tech/vendor", "Stackable"),
	])
	.unwrap();
	assert_eq!(labels.len(), 2);
	}

for a small example.

[NickLarsenNZ]

Nice one! This is immediately useful (thought probably in the next round of operator maintenance)

[NickLarsenNZ]

Nicely done 🚀

[NickLarsenNZ]

👍