[internal] upgrade toolchain pants plugin to 0.12.0 (pantsbuild#12168)

Notable changes:

* Fix issue with decoding tokens (handle missing padding)
* Simplify config (single location for base url)
* Exclude environment variables that might contain secrets or sensitive data
* Buildsense now enabled by default.

pants.ci.toml

@@ -23,8 +23,8 @@ report = ["raw", "xml"]
 from_env_var = "TOOLCHAIN_AUTH_TOKEN"
 org = "pantsbuild"
 ci_env_variables = [
-  "TRAVIS", "TRAVIS_JOB_ID", "TRAVIS_BUILD_ID", "TRAVIS_PULL_REQUEST", "TRAVIS_BUILD_WEB_URL",
   "GITHUB_ACTIONS", "GITHUB_RUN_ID", "GITHUB_REF", "GITHUB_EVENT_NAME", "GITHUB_SHA", "GITHUB_REPOSITORY",
+  "GITHUB_WORKFLOW","GITHUB_JOB",  # temporary, for debugging issues w/ restricted tokens.
 ]
 restricted_token_matches =  """{
   'GITHUB_REPOSITORY': 'pantsbuild/pants', 

pants.toml

@@ -20,7 +20,7 @@ backend_packages.add = [
 ]
 plugins = [
   "hdrhistogram",  # For use with `--stats-log`.
-  "toolchain.pants.plugin==0.11.0",
+  "toolchain.pants.plugin==0.12.0",
 ]
 
 # The invalidation globs cover the PYTHONPATH by default, but we exclude some files that are on the
@@ -173,3 +173,6 @@ config = "@build-support/regexes/config.yaml"
 
 [toolchain-setup]
 repo = "pants"
+
+[buildsense]
+enable = false