Fix chained expressions

[unlessgames]

Chained expressions were generating unexpectedly thrown away results thanks to the way they were parsed, fixing that here.

Also did a bit of cleanup by separated the Target, Bjorklund and Degrade operators from Dynamic/Dynamic Op/Expression, as they were treated special anyway, this makes the types better reflect the behaviour and leads to a bit less branching at the cost of a few more types.

A few more test cases would be nice to add before merge.

[github-actions]

Benchmark for 73cd84b

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	49.2±0.40µs	52.6±0.57µs	+6.91%
Cycle/Parse	366.2±5.92µs	350.8±7.16µs	-4.21%
Rust Phrase/Clone	443.9±22.47ns	445.8±7.27ns	+0.43%
Rust Phrase/Create	71.4±1.40µs	71.8±1.39µs	+0.56%
Rust Phrase/Run	642.7±8.15µs	657.2±5.69µs	+2.26%
Rust Phrase/Seek	150.6±281.26µs	151.8±283.19µs	+0.80%
Scripted Phrase/Clone	619.2±9.10ns	623.9±8.08ns	+0.76%
Scripted Phrase/Create	956.9±12.92µs	959.5±8.35µs	+0.27%
Scripted Phrase/Run	1666.1±7.94µs	1676.1±13.96µs	+0.60%
Scripted Phrase/Seek	216.0±436.10µs	213.3±429.60µs	-1.25%

[github-actions]

Benchmark for d82248e

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	48.9±0.35µs	49.4±0.36µs	+1.02%
Cycle/Parse	362.8±4.75µs	354.2±6.89µs	-2.37%
Rust Phrase/Clone	434.6±9.76ns	443.3±5.24ns	+2.00%
Rust Phrase/Create	71.6±1.24µs	73.2±2.09µs	+2.23%
Rust Phrase/Run	632.6±6.69µs	631.8±5.04µs	-0.13%
Rust Phrase/Seek	146.2±271.87µs	146.9±272.84µs	+0.48%
Scripted Phrase/Clone	626.4±8.20ns	618.8±5.06ns	-1.21%
Scripted Phrase/Create	950.7±8.14µs	959.4±11.43µs	+0.92%
Scripted Phrase/Run	1649.0±9.96µs	1628.5±21.21µs	-1.24%
Scripted Phrase/Seek	221.1±447.13µs	211.6±426.74µs	-4.30%

[github-actions]

Benchmark for bcfdb47

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	48.7±0.51µs	48.7±0.46µs	0.00%
Cycle/Parse	363.4±5.88µs	363.9±5.56µs	+0.14%
Rust Phrase/Clone	430.4±5.07ns	434.0±4.74ns	+0.84%
Rust Phrase/Create	71.7±1.17µs	73.9±2.68µs	+3.07%
Rust Phrase/Run	641.7±5.36µs	647.6±3.97µs	+0.92%
Rust Phrase/Seek	144.1±268.90µs	141.9±265.01µs	-1.53%
Scripted Phrase/Clone	613.0±11.00ns	613.1±4.86ns	+0.02%
Scripted Phrase/Create	971.2±13.92µs	961.5±12.87µs	-1.00%
Scripted Phrase/Run	1617.8±14.39µs	1625.4±6.74µs	+0.47%
Scripted Phrase/Seek	217.6±441.03µs	201.9±403.57µs	-7.22%

[unlessgames]

So this seems ok, added some tests, found and fixed a bug in the meantime.

If it looks good we should merge it as I have other stuff in the works that rely on this PR.

[emuell]

Looks all good to me. Will do more testing after this got merged...