[Feature Request] Add a JsonWebToken Constructor that accepts ReadOnlyMemory representation of the encodedToken

[sruke]

Is your feature request related to a problem? Please describe.
The usage of String.Split to extract segments from the token is expensive as it creates new strings and leads to additional memory allocation.

Describe the solution you'd like

• Introduce a JsonWebToken Constructor that accepts ReadOnlyMemory representation of the encodedToken. This would allow us to substitute string.Split with span.Slice which will avoid string creation.
• Update existing constructors to call into ReadTokens(ReadOnlyMemory) to maintain a single code path and enable current implementations to take advantage of some of the improvements without making any changes.

[Saibamen]

I would love to see benchmarks

[sruke]

I would love to see benchmarks

Added benchmarks in the PR that I just linked to the GitHub issue and in the discussion board where a preview has been shared. Appreciate any feedback.

@Saibamen ^