wip: implement encodable for terminator manually to save a byte

[panstromek]

No description provided.

[panstromek]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: c122edf (c122edf56b6e372444080d056db3e4dea07bcf2e)
Base parent: 7088e4b (7088e4b63a9516ebfbfe2ab2d999cf01a528ac14)

[rust-timer]

Finished benchmarking commit (c122edf): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This perf run didn't have relevant results for this metric.

Max RSS (memory usage)

Results (secondary 1.3%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.9%	[2.0%, 6.9%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.9%, -0.5%]	4
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary 0.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.8%	[0.4%, 2.3%]	12
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-1.5%, -0.4%]	7
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.3%, secondary -0.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.3%	[-0.7%, -0.0%]	72
Improvements ✅ (secondary)	-0.5%	[-1.3%, -0.0%]	73
All ❌✅ (primary)	-0.3%	[-0.7%, -0.0%]	72

Bootstrap: 455.179s -> 454.771s (-0.09%)
Artifact size: 398.37 MiB -> 398.40 MiB (0.01%)

[rust-bors]

☔ The latest upstream changes (presumably #162827) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.