fix(gotemplate-helm): toToml emits Go BurntSushi-style tables (#490 bucket 3)

[alexmond]

Closes bucket 3 of #490. HelmConformanceTest backlog now 37 → 1.

toToml serialised via Jackson's TomlMapper, which writes nested maps as dotted keys (mast.sail = "white"), whereas Helm's Go BurntSushi encoder emits [table] headers. New TomlWriter reproduces BurntSushi's output, reverse-engineered from the helm binary:

• keys sorted alphabetically; scalar / inline-array fields before sub-tables
• table key/values indented depth*2, [header] indented (depth-1)*2
• a blank line before every top-level table and every array-of-tables element (never before the first output line)
• basic (double-quoted) strings; floats always carry a decimal point

{mast: {sail: white}}              ->  [mast]
                                         sail = "white"

{a: {xx: v, bb: {cc: deepval}}}    ->  [a]
                                         xx = "v"
                                         [a.bb]
                                           cc = "deepval"

Replaces the Jackson serialisation and the now-dead tomlToGoStyle single→double-quote post-process for both toToml and mustToToml; fromToml still parses via TomlMapper. Adds nested-table + array-of-tables unit tests asserting the exact helm output.

Remaining (1 divergence)

Only fromToml "one" stays pinned — a true TOML syntax error whose exact BurntSushi wording (toml: line 1: unexpected EOF; expected key separator '=') a Jackson parser can't reproduce without overfitting.

Verification

• jhelm-gotemplate-helm verify green — 131 tests, spring-javaformat / PMD / Checkstyle
• 346/346 chart byte-parity unchanged (no chart uses toToml)

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[github-actions]

Overall Project	81.38%	🍏

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Codecov Report

❌ Patch coverage is 62.50000% with 36 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...nd/jhelm/gotemplate/helm/functions/TomlWriter.java	61.70%	27 Missing and 9 partials ⚠️

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[github-actions]

Overall Project	81.38%	🍏

There is no coverage information present for the Files changed