[browser] Split dotnet.js and introduce loader + emscripten modules

[maraf]

Split dotnet.js into a smallest possible loader that is fast to load and allows to

• Detect wasm features and allow to load variants of emscripten and wasm files
• Provide "not often changing" unit, that doesn't need fingerprint

The rest of the code, mostly emscripten, that can change based on supported features, etc, will be downloaded in parallel with other assets

cc @pavelsavara @radical

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Issue Details

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Split dotnet.js into a smallest possible loader that is fast to load and allows to

• Detect wasm features and allow to load variants of emscripten and wasm files
• Provide "not often changing" unit, that doesn't need fingerprint

cc @pavelsavara @radical

Author:	maraf
Assignees:	-
Labels:	arch-wasm, area-Build-mono
Milestone:	8.0.0

[maraf]

Closed in #85730