fix: correctly turn on optional opentelemetry dependencies (#25)

## Motivation

Newer opentelemetry features were wrong as they did not enable all
needed dependencies causing compilation failures.

Closes #24 

## Solution

Correctly enable all needed dependencies.

Also, create new features for the implicit features that were mistakenly
added. This is needed in case someone found the bug and simply worked
around it by enabling these features so that we do not break them in a
patch release. These are to be deleted with then next breaking changes.

Author: mladedav

Cargo.toml

@@ -23,6 +23,20 @@ tracing-opentelemetry-0-29 = [
     "dep:tracing-opentelemetry-0-29",
     "dep:opentelemetry-0-28",
 ]
+tracing-opentelemetry-0-30 = [
+    "dep:tracing-opentelemetry-0-30",
+    "dep:opentelemetry-0-29",
+]
+tracing-opentelemetry-0-31 = [
+    "dep:tracing-opentelemetry-0-31",
+    "dep:opentelemetry-0-30",
+]
+
+# TODO Remove this for the next breaking release.
+# This is the price I have to pay to the gods of semantic versioning for failing to notice I created
+# unintended implicit features.
+opentelemetry-0-29 = ["dep:opentelemetry-0-29"]
+opentelemetry-0-30 = ["dep:opentelemetry-0-30"]
 
 # Required for intra-doc links to resolve correctly
 __private_docs = ["tracing-subscriber/time", "tracing-subscriber/local-time"]
@@ -50,7 +64,7 @@ opentelemetry-0-27 = { package = "opentelemetry", version = "0.27.0", default-fe
 tracing-opentelemetry-0-29 = { package = "tracing-opentelemetry", version = "0.29.0", default-features = false, optional = true }
 opentelemetry-0-28 = { package = "opentelemetry", version = "0.28.0", default-features = false, optional = true }
 tracing-opentelemetry-0-30 = { package = "tracing-opentelemetry", version = "0.30.0", default-features = false, optional = true }
-opentelemetry-0-29 = { package = "opentelemetry", version = "0.29.0", default-features = false, optional = true }
+opentelemetry-0-29 = { package = "opentelemetry", version = "0.29.0", default-features = false, features = ["futures"], optional = true }
 tracing-opentelemetry-0-31 = { package = "tracing-opentelemetry", version = "0.31.0", default-features = false, optional = true }
 opentelemetry-0-30 = { package = "opentelemetry", version = "0.30.0", default-features = false, optional = true }