chore(gatsby): add environment variable for setting tracing config file (gatsbyjs#32513)

* chore: add option for openTracingConfigFile env

* chore: format

* Standardize env variable name + document

Co-authored-by: gatsbybot <mathews.kyle+gatsbybot@gmail.com>
Co-authored-by: Kyle Mathews <mathews.kyle@gmail.com>

Author: 3 people

yarn.lock

@@ -1871,16 +1871,21 @@
     "@types/node" "*"
     form-data "^3.0.0"
 
-"@types/node@*", "@types/node@^8.5.7":
-  version "8.10.66"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-8.10.66.tgz#dd035d409df322acc83dff62a602f12a5783bbb3"
-  integrity sha512-tktOkFUA4kXx2hhhrB8bIFb5TbwzS4uOhKEmwiD+NoiL0qtP2OQ9mFldbgD4dV1djrlBYP6eBuQZiWjuHUpqFw==
+"@types/node@*":
+  version "16.4.12"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-16.4.12.tgz#961e3091f263e6345d2d84afab4e047a60b4b11b"
+  integrity sha512-zxrTNFl9Z8boMJXs6ieqZP0wAhvkdzmHSxTlJabM16cf5G9xBc1uPRH5Bbv2omEDDiM8MzTfqTJXBf0Ba4xFWA==
 
 "@types/node@^14.14.10":
   version "14.17.14"
   resolved "https://registry.yarnpkg.com/@types/node/-/node-14.17.14.tgz#6fda9785b41570eb628bac27be4b602769a3f938"
   integrity sha512-rsAj2u8Xkqfc332iXV12SqIsjVi07H479bOP4q94NAcjzmAvapumEhuVIt53koEf7JFrpjgNKjBga5Pnn/GL8A==
 
+"@types/node@^8.5.7":
+  version "8.10.66"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-8.10.66.tgz#dd035d409df322acc83dff62a602f12a5783bbb3"
+  integrity sha512-tktOkFUA4kXx2hhhrB8bIFb5TbwzS4uOhKEmwiD+NoiL0qtP2OQ9mFldbgD4dV1djrlBYP6eBuQZiWjuHUpqFw==
+
 "@types/parse-json@^4.0.0":
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/@types/parse-json/-/parse-json-4.0.0.tgz#2f8bb441434d163b35fb8ffdccd7138927ffb8c0"