Initialize conversion of ci_build_trace_chunks.build_id to bigint

What does this MR do?

This MR starts conversion of ci_build_trace_chunks.build_id to bigint.

See to #328442 (closed).

Database migrations

Up

$ bundle exec rails db:migrate
== 20210427045604 InitializeConversionOfCiBuildTraceChunksToBigint: migrating =
-- table_exists?(:ci_build_trace_chunks)
   -> 0.0015s
-- column_exists?(:ci_build_trace_chunks, :id)
   -> 0.0015s
-- column_exists?(:ci_build_trace_chunks, :build_id)
   -> 0.0009s
-- columns(:ci_build_trace_chunks)
   -> 0.0011s
-- add_column(:ci_build_trace_chunks, "build_id_convert_to_bigint", :bigint, {:default=>0, :null=>false})
   -> 0.0045s
== 20210427045604 InitializeConversionOfCiBuildTraceChunksToBigint: migrated (0.0304s) 

== 20210427045711 BackfillCiBuildTraceChunksForBigintConversion: migrating ====
-- table_exists?(:ci_build_trace_chunks)
   -> 0.0014s
-- column_exists?(:ci_build_trace_chunks, :id)
   -> 0.0012s
-- column_exists?(:ci_build_trace_chunks, :build_id)
   -> 0.0009s
-- column_exists?(:ci_build_trace_chunks, "build_id_convert_to_bigint")
   -> 0.0010s
unknown OID 28: failed to recognize type of 'relfrozenxid'. It will be treated as String.
unknown OID 1034: failed to recognize type of 'relacl'. It will be treated as String.
unknown OID 194: failed to recognize type of 'relpartbound'. It will be treated as String.
== 20210427045711 BackfillCiBuildTraceChunksForBigintConversion: migrated (0.0546s) 

Down

$ bundle exec rails db:migrate:down VERSION=20210427045711
== 20210427045711 BackfillCiBuildTraceChunksForBigintConversion: reverting ====
-- execute("DELETE FROM batched_background_migrations WHERE job_class_name = 'CopyColumnUsingBackgroundMigrationJob' AND table_name = 'ci_build_trace_chunks' AND column_name = 'id' AND job_arguments = '[[\"build_id\"],[\"build_id_convert_to_bigint\"]]'")
   -> 0.0036s
== 20210427045711 BackfillCiBuildTraceChunksForBigintConversion: reverted (0.0038s) 

$ bundle exec rails db:migrate:down VERSION=20210427045604
== 20210427045604 InitializeConversionOfCiBuildTraceChunksToBigint: reverting =
-- remove_column(:ci_build_trace_chunks, "build_id_convert_to_bigint")
   -> 0.0012s
== 20210427045604 InitializeConversionOfCiBuildTraceChunksToBigint: reverted (0.0047s) 

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