urlencoding dependency removal

[cijothomas]

See https://github.com/open-telemetry/opentelemetry-rust/pull/1578#discussion_r1507777504

[stormshield-fabs]

For context, https://github.com/open-telemetry/opentelemetry-rust/pull/1578 added support for percent-encoded OTEL_EXPORTER* environment variables. It was proposed to remove the urlencoding crate that indicated it's looking for a maintainer.

The specification states that "these are expected to be represented in a format matching to the W3C Baggage" (link to the exporter specification). The Baggage specification indicates that

Percent-encoding is defined in [RFC3986], Section 2.1: https://datatracker.ietf.org/doc/html/rfc3986#section-2.1

I was about to propose Servo's percent_encoding but it turns out it does not implement RFC3986.

[TommyCpp]

close via #1615