Enhance: TypeScriptの型を厳格化

[takejohn]

What

• asや!による型アサーションを減らします。
• CharStreamのeofやcharがgetterであるために意図しないnarrowingが発生していたので通常のメソッドに変更します。
• パーサのプラグインで用いるvisitNode関数にジェネリクスを使用します。
• Ast.Forの型を変更し、(varおよびfrom, to)またはtimesのどちらかが必須となるようにします。
• Tokenの型を変更し、識別子やリテラルの場合はvalueを、テンプレートリテラルの場合はchildrenを必須にします。

Why

Resolve #880

Additional info (optional)

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 98.93238% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/error.ts	66.66%	2 Missing :warning:
src/interpreter/index.ts	96.96%	1 Missing :warning:

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Files with missing lines	Coverage Δ
src/interpreter/primitive-props.ts	98.07% <100.00%> (+0.09%)	:arrow_up:
src/interpreter/scope.ts	93.69% <100.00%> (+3.15%)	:arrow_up:
src/node.ts	85.71% <ø> (-12.66%)	:arrow_down:
src/parser/plugins/validate-jump-statements.ts	100.00% <100.00%> (ø)
src/parser/plugins/validate-keyword.ts	95.67% <100.00%> (+7.06%)	:arrow_up:
src/parser/plugins/validate-type.ts	100.00% <100.00%> (+17.64%)	:arrow_up:
src/parser/scanner.ts	95.22% <100.00%> (+6.46%)	:arrow_up:
src/parser/streams/char-stream.ts	90.47% <100.00%> (+1.98%)	:arrow_up:
src/parser/streams/token-stream.ts	79.62% <ø> (+16.18%)	:arrow_up:
src/parser/syntaxes/common.ts	96.82% <100.00%> (+7.29%)	:arrow_up:
... and 9 more

... and 13 files with indirect coverage changes