Remove extensions method from BCL classes

[Kielek]

Feature Request

Remove extensions methods related to the BCL (string!) classes. It could be noisy for Intellisense,

Describe the solution you'd like:

Consider methods like

internal static JaegerExportProtocol? ParseProtocol(string value)

or

internal static bool ParseProtocol(string value, out JaegerExportProtocol result)

instead of

public static JaegerExportProtocol? ToJaegerExportProtocol(this string protocol) =>

Describe alternatives you've considered.

Which alternative solutions or features have you considered?

Additional Context

Based on #2875 (comment) and #2914 (review)