[pkg/ottl] Add SpanEvent context (open-telemetry#14907)

* Add SpanEvent context

* add changelog entry and fix lint

* ran make goporto

* Apply feedback

* Fix test

* Share span symbol table

* fix lint

* Rename to ottlspanevent

.chloggen/ottl-spanevents-context.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add new Span Event context to allow for efficient transformation of Span Event telemetry.
+
+# One or more tracking issues related to the change
+issues: [14907]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: