1. support read and write null in segcore
will store valid_data(use uint8_t type to save memory) in fieldData.
2. support load null
binlog reader read and write data into column(sealed segment),
insertRecord(growing segment). In sealed segment, store valid_data
directly. In growing segment, considering prior implementation and easy
code reading, it covert uint8_t to fbvector<bool>, which may optimize in
future.
3. retrieve valid_data.
parse valid_data in search/query.
#31728
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Signed-off-by: lixinguo <xinguo.li@zilliz.com>
Co-authored-by: lixinguo <xinguo.li@zilliz.com>
