BigQuery: Add ALTER VIEW

[yoichi]

Brief summary of the change made

fixes #4293

Are there any other side effects of this change that we should be aware of?

No

Pull Request checklist

• Please confirm you have completed any of the necessary steps below.

• Included test cases to demonstrate any code changes, which may be one or more of the following:

  • .yml rule test cases in test/fixtures/rules/std_rule_cases.
  • .sql/.yml parser test cases in test/fixtures/dialects (note YML files can be auto generated with tox -e generate-fixture-yml).
  • Full autofix test cases in test/fixtures/linter/autofix.
  • Other.

• Added appropriate documentation for the change.

• Created GitHub issues for any relevant followup/future enhancements if appropriate.

[coveralls]

Pull Request Test Coverage Report for Build 3978695147

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 3970453897:	0.0%
Covered Lines:	17075
Relevant Lines:	17075

---

💛 - Coveralls

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (41c70d4) compared to base (b5ca7eb).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #4306   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          201       201           
  Lines        15278     15281    +3     
=========================================
+ Hits         15278     15281    +3     

Impacted Files	Coverage Δ
src/sqlfluff/dialects/dialect_bigquery.py	100.00% <100.00%> (ø)

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[WittierDinosaur]

LGTM