[browser] Pass configured config name to loadBootResource

[maraf]

Before this change, we were always passing "blazor.boot.json" to as name to loadBootResource. If someone uses it to construct the URL, like aspnetcore tests, it creates an incorrect URL.

Contributes to dotnet/aspnetcore#59456

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PR Overview

This PR changes the way the boot configuration file is resolved by passing the configured config name to loadBootResource instead of a hard-coded value. Key changes include updating the fallback config path, passing module.configSrc and its resolved URL to loadBootResource, and switching from using defaultConfigSrc to defaultConfigUrl when checking for JSON resources.

Reviewed Changes

File	Description
src/mono/browser/runtime/loader/config.ts	Update fallback configuration value and resource loading functions to use the configured config name and corresponding URL

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src/mono/browser/runtime/loader/config.ts:246

• The fallback configuration value has been changed from "./blazor.boot.json" to "blazor.boot.json". Please verify that removing the './' prefix is intentional, as it might affect how the relative path is resolved.

?? "blazor.boot.json";