fork OTEL-Rust and OTLP

Clean import of OTEL-rust (https://github.com/open-telemetry/opentelemetry-rust) and OTLP (https://github.com/open-telemetry/opentelemetry-proto) before local modifications are applied. This should be a precursor CL to https://oak-review.git.corp.google.com/c/oak/+/6920 and https://oak-review.git.corp.google.com/c/oak/+/6981.

This is needed for Restricted Kernel Metrics (https://docs.google.com/document/d/18YytPP1yBRe8kLBVJ8A6JefGfQ-c4sUQHQTixAYl0BE/edit?resourcekey=0-vdWLnvxpPQlZtVZGEW39MA&tab=t.0#heading=h.xzptrog8pyxf), as versions of Opentelemetry/Opentelemetry Protocol which are no_std and microRPC compatible, respectively, will be necessary,

#OakObservability

Change-Id: Ic1f38e31f2ffe8025c416be6f8d6645e9b4565e2

third_party/opentelemetry/opentelemetry-proto/.gitattributes

@@ -0,0 +1 @@
+* text=auto eol=lf

third_party/opentelemetry/opentelemetry-proto/.gitignore

@@ -0,0 +1,24 @@
+# IntelliJ IDEA
+.idea
+*.iml
+
+# VS Code
+.vscode
+.classpath
+.project
+.settings/
+
+# OS X
+.DS_Store
+
+# Emacs
+*~
+\#*\#
+
+# Vim
+.swp
+
+# Generated code
+/gen/
+
+node_modules

third_party/opentelemetry/opentelemetry-proto/.markdown_link_check_config.json

@@ -0,0 +1,22 @@
+{
+  "ignorePatterns": [
+    {
+      "pattern": "^https://github\\.com/open-telemetry/opentelemetry-specification/(issues|pull)"
+    }
+  ],
+  "replacementPatterns": [
+    {
+      "pattern": "^/",
+      "replacement": "{{BASEURL}}/"
+    },
+    {
+      "pattern": "^https://github.com/open-telemetry/opentelemetry-proto/(blob|tree)/[^/]+/docs/",
+      "replacement": "LINK-CHECK-ERROR-USE-LOCAL-PATH-TO-DOC-PAGE-NOT-EXTERNAL-URL/"
+    }
+  ],
+  "retryOn429": true,
+  "aliveStatusCodes": [
+    200,
+    403
+  ]
+}

third_party/opentelemetry/opentelemetry-proto/.markdownlint.yaml

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+# See https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md
+# and https://github.com/DavidAnson/markdownlint/blob/main/README.md
+
+# Default state for all rules
+default: true
+
+ul-style: false
+line-length: false
+no-duplicate-header:
+  siblings_only: true
+ol-prefix:
+  style: ordered
+no-inline-html: false
+fenced-code-language: false