chore: move bigframes package to separate repo (#18091)

https://github.com/google/bigframes is the new location for bigframes.

See internal issue b/517198791
🦕

(See below to close bigframes related PRs)
Closes #17502
Closes #17837
Closes #17587
Closes #17595
Closes #18095
Closes #18096
Closes #18109
Closes #18110
Closes #18113
Closes #18125
Closes #17587

Author: tswast

.github/CODEOWNERS

@@ -28,7 +28,6 @@
 # Catch all. @googleapis/cloud-sdk-python-team is notified on every change for packages not owned by other teams.
 *                                             @googleapis/cloud-sdk-python-team
 
-/packages/bigframes/                          @googleapis/bigquery-team @googleapis/bigquery-dataframe-team
 /packages/bigquery-magics/                    @googleapis/bigquery-team @googleapis/bigquery-dataframe-team
 /packages/db-dtypes/                          @googleapis/bigquery-team @googleapis/bigquery-dataframe-team
 /packages/django-google-spanner/              @googleapis/spanner-team

.github/workflows/bigframes-docs-deploy.yaml

@@ -36,7 +36,6 @@ jobs:
       # Each weight is roughly 1 minute of expected execution time
       # Default for unset packages is 1
       PACKAGE_WEIGHTS: |
-        bigframes: 6
         google-ai-generativelanguage: 4
         google-auth: 5
         google-cloud-compute: 12

.github/workflows/unittest.yml

@@ -5,8 +5,3 @@ env_vars: {
     key: "NOX_SESSION"
     value: "prerelease_deps"
 }
-
-env_vars: {
-  key: "BIGFRAMES_TEST_PROJECT"
-  value: "bigframes-load-testing"
-}

.kokoro/continuous/benchmark-bigframes.cfg

@@ -5,8 +5,3 @@ env_vars: {
     key: "NOX_SESSION"
     value: "system-3.12"
 }
-
-env_vars: {
-  key: "BIGFRAMES_TEST_PROJECT"
-  value: "bigframes-load-testing"
-}