docs: Convert _all_ the intra-doc links (#1022)

## Motivation

Closes tokio-rs/tracing#940.

## Solution

Uses ~~a heavily patched version~~ the latest master version of
https://github.com/poliorcetics/cargo-intraconv/ to automatically
convert the links. Fixes remaining issues by hand.

Author: jyn514

tracing-opentelemetry/src/tracer.rs

@@ -20,12 +20,11 @@ use opentelemetry::{api, sdk};
 /// See the [`OpenTelemetrySpanExt::set_parent`] and
 /// [`OpenTelemetrySpanExt::context`] methods for example usage.
 ///
+/// [`OpenTelemetrySpanExt::set_parent`]: crate::OpenTelemetrySpanExt::set_parent
+/// [`OpenTelemetrySpanExt::context`]: crate::OpenTelemetrySpanExt::context
 /// [`Tracer`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/tracer/trait.Tracer.html
 /// [`SpanBuilder`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/tracer/struct.SpanBuilder.html
 /// [`SpanContext`]: https://docs.rs/opentelemetry/latest/opentelemetry/api/trace/span_context/struct.SpanContext.html
-/// [`PreSampledTracer::sampled_span_context`]: trait.PreSampledTracer.html#tymethod.sampled_span_context
-/// [`OpenTelemetrySpanExt::set_parent`]: trait.OpenTelemetrySpanExt.html#tymethod.set_parent
-/// [`OpenTelemetrySpanExt::context`]: trait.OpenTelemetrySpanExt.html#tymethod.context
 pub trait PreSampledTracer {
     /// Produce a pre-sampled span context for the given span builder.
     fn sampled_span_context(&self, builder: &mut api::SpanBuilder) -> api::SpanContext;