Rename ISpan and ITransaction

[jamescrosswell]

ISpan might be more appropriately named ISpanTracer since it represents properties and methods that are only implemented by SpanTracer and TransactionTracer.

For the same reason, ITransaction could be more appropriately named ITransactionTracer.

See entity relationship diagram below:

erDiagram
    NoOpSpan ||--|| ISpan : implements

    SpanTracer ||--|| ISpan : implements
    SpanTracer {
        bool IsSentryRequest
        TransactionTracer Transaction
        void Unfinish()
    }


    ISpan ||--|| ISpanData : implements
    ISpan {
        string Description
        string Operation
        SpanStatus Status
        ISpan StartChild()
        void Finish()
    }

    Span ||--|| ISpanData : implements

    ISpanData ||--|| ITraceContext : implements
    ISpanData ||--|| IHasTags : implements
    ISpanData ||--|| IHasExtra : implements
    ISpanData {
        DateTimeOffset StartTimestamp
        DateTimeOffset EndTimestamp
        bool IsFinished
        SentryTraceHeader GetTraceHeader()
    }

    NoOpTransaction ||--|| ITransaction : implements

    TransactionTracer ||--|| ISpan : implements
    TransactionTracer ||--|| ITransaction : implements
    TransactionTracer ||--|| ITransactionData : implements
    TransactionTracer ||--|| ISpan : implements
    TransactionTracer {
        bool IsSentryRequest
        double SampleRate
        IReadOnlyCollection Spans
        DynamicSamplingContext DynamicSamplingContext
        ITransactionProfiler TransactionProfiler
        void AddChildSpan()
        ISpan GetLastActiveSpan()
    }

    ITransaction ||--|| ITransactionData : implements
    ITransaction ||--|| ISpan : implements
    ITransaction {
        string Name
        bool IsParentSampled
        IReadOnlyCollection Spans
        ISpan GetLastActiveSpan()
    }

    Transaction ||--|| ITransactionData : implements
    Transaction {
        SentryId EventId
        double SampleRate
        DynamicSamplingContext DynamicSamplingContext
        ITransactionProfiler TransactionProfiler
        IReadOnlyCollection Spans
        void Redact()
        void WriteTo()
        Transaction FromJson()
    }

    ITransactionData ||--||  ISpanData : implements
    ITransactionData ||--|| ITransactionContext : implements
    ITransactionData ||--|| IEventLike : implements

    ITransactionContext ||--|| ITraceContext : implements

    IEventLike ||--|| IHasTags : implements
    IEventLike ||--|| IHasExtra : implements

    TransactionContext ||--|| SpanContext : implements
    TransactionContext ||--|| ITransactionContext : implements

    SpanContext ||--|| ITraceContext : implements

Loading

[bitsandfoxes]

Worth considering #1491 while we're at it.