Relax the checks for the presence of ArrowSchema.name as this field is optional

[Qqwy]

As per the spec, the ArrowSchema.name field is optional. SQLite is an example of a producer which does not set this field.

This PR removes the checks on this field, returning an empty string if the field is NULL for backwards compatibility.

[codecov[bot]]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.03 :warning:

Comparison is base (fb5e4d5) 83.61% compared to head (6be098c) 83.59%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1499 +/- ## ========================================== - Coverage 83.61% 83.59% -0.03% ========================================== Files 388 388 Lines 41910 41912 +2 ========================================== - Hits 35043 35035 -8 - Misses 6867 6877 +10 ``` | [Impacted Files](https://app.codecov.io/gh/jorgecarleitao/arrow2/pull/1499?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jorge+Leitao) | Coverage Δ | | |---|---|---| | [src/ffi/schema.rs](https://app.codecov.io/gh/jorgecarleitao/arrow2/pull/1499?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jorge+Leitao#diff-c3JjL2ZmaS9zY2hlbWEucnM=) | `90.28% <66.66%> (-0.17%)` | :arrow_down: | ... and [5 files with indirect coverage changes](https://app.codecov.io/gh/jorgecarleitao/arrow2/pull/1499/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jorge+Leitao)

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[Qqwy]

@sundy-li The formatter CI pass should now also succeed.