chore(main): release 2.20.0

[release-please]

🤖 I have created a release beep boop

2.20.0 (2025-09-16)

Features

• Add __dataframe__ interchange support (#2063) (3b46a0d)
• Add ai_generate_bool to the bigframes.bigquery package (#2060) (70d6562)
• Add bigframes.bigquery.to_json_string (#2076) (41e8f33)
• Add rank(pct=True) support (#2084) (c1e871d)
• Add StreamingDataFrame.to_bigtable and .to_pubsub start_timestamp parameter (#2066) (a63cbae)
• Can call agg with some callables (#2055) (17a1ed9)
• Support astype to json (#2073) (6bd6738)
• Support pandas.Index as key for DataFrame.setitem() (#2062) (b3cf824)
• Support pd.cut() for array-like type (#2064) (21eb213)
• Support to cast struct to json (#2067) (b0ff718)

Bug Fixes

• Deflake ai_gen_bool multimodel test (#2085) (566a37a)
• Do not scroll page selector in anywidget repr_mode (#2082) (5ce5d63)
• Fix the potential invalid VPC egress configuration (#2068) (cce4966)
• Return a DataFrame containing query stats for all non-SELECT statements (#2071) (a52b913)
• Use the remote and managed functions for bigframes results (#2079) (49b91e8)

Performance Improvements

• Avoid re-authenticating if credentials have already been fetched (#2058) (913de1b)
• Improve apply axis=1 performance (#2077) (12e4380)

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