Sort switch cases by value; coalesce identical-body cases

[AaronWebster]

Three composing changes to the optimized Ok() switch generator:

1. Case-label sort. Each switch arm's labels are sorted by underlying integer/enum value before emit. Sorted cases give older embedded GCCs (the ones in microblaze-elf and many bare-metal arm-none-eabi toolchains) a better shot at emitting a dense jump table rather than an if-ladder.

2. Identical-body coalescing. Cases whose rendered body text is identical are merged into a single arm with multiple case X: labels. The C++ compiler emits one body for the whole arm — a real text-size win once the next PR (disjunction matching) starts producing such pairs.

3. Multi-field per case. When two conditional fields share a discriminant + case value (if tag == 0: a and if tag == 0: b), they bundle into the same case arm rather than the second falling back to a separate if-statement.

The ok_method_switch_case template becomes ok_method_switch_arm taking pre-formatted ${case_labels} and ${case_body} strings. Single-label single-field arms render identically, so golden churn is limited to the f0_copy field in testdata/many_conditionals.emb folding into case 0 of the LargeConditionals switch.

Size impact (cumulative vs. master)

Target	Metric	Master	PR	Delta
ARM Thumb-2	TU .text	18962	18296	−666 (−3.5%)
ARM Thumb-2	LargeConditionals::Ok()	5382	4746	−636 (−11.8%)
MicroBlaze	TU .text	43640	42700	−940 (−2.2%)
MicroBlaze	LargeConditionals::Ok()	14824	14104	−720 (−4.9%)
Host x86-64	TU .text	29166	28344	−822 (−2.8%)
Host x86-64	LargeConditionals::Ok()	3948	3065	−883 (−22.4%)

Stacked on #253.