feat!: rename getHighlighter to createHighlighter

[antfu]

The function name getHighlighter, inherited from Shiki v0.x, which is somehow confusing. While it is supposed to be a singleton, we see people using it incorrectly in components or loops:

• "TypeError: onigBinding.UTF8ToString is not a function" after some time / parallel requests in Next.js #693
• RuntimeError: memory access out of bounds #567

While we improved the docs in 412fe10, I think the confusing still down to the name prefix get reads like it will retrieve the global instance, while it actually not. In the actual behavior, it's more like create a new instance every time calling the function, thus this PR propose renaming:

• getHighlighter to createHighlighter
• getHighlighterCore to createHighlighterCore
• getShikiInternal to createShikiInternal

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Alternatively, we encourage users to use getSingletonHighlighter instead, where it holds the singleton instance underneath, and loads new themes/languages automatically.

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Changes rolling out plan

• v1.9.0 will introduce createHighlighter getSingletonHighlighter functions. All docs change to create* version. APIs like getHighlighter are shims to behave like before, but marked as deprecate on the type level.
• v1.10.0+ warning messages will be print at runtime when using getHighlighter etc.
• v2.0.0 Deprecated APIs will be removed (breaking changes)

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[codecov]

Codecov Report

Attention: Patch coverage is 90.55118% with 12 lines in your changes missing coverage. Please review.

Project coverage is 96.31%. Comparing base (2468337) to head (850a2a7).

Files	Patch %	Lines
packages/core/src/bundle-factory.ts	94.11%	3 Missing ⚠️
packages/core/src/internal.ts	66.66%	3 Missing ⚠️
packages/shiki/src/bundle-full.ts	72.72%	3 Missing ⚠️
packages/shiki/src/bundle-web.ts	72.72%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #702      +/-   ##
==========================================
- Coverage   96.45%   96.31%   -0.14%     
==========================================
  Files          70       70              
  Lines        5984     6056      +72     
  Branches      799      805       +6     
==========================================
+ Hits         5772     5833      +61     
- Misses        207      218      +11     
  Partials        5        5              

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