Adds SpanFilter as a configuration option

[fantapop]

SpanFilter is a custom function that can be passed via configuration to control whether any given span should be included or omitted. (#169)

Example usage:

otelsql.SpanOptions{
    // Skip creating spans which don't have a parent
    SpanFilter: func(ctx context.Context, method otelsql.Method, query string, args []driver.NamedValue) bool {
        span := trace.SpanFromContext(ctx)
        return span.SpanContext().IsValid()
    },
}

[codecov]

Codecov Report

Patch coverage: 100.0% and project coverage change: +0.5 🎉

Comparison is base (2956a1e) 80.0% compared to head (d5d3bd3) 80.5%.

❗ Current head d5d3bd3 differs from pull request most recent head dec9ce3. Consider uploading reports for the commit dec9ce3 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #174     +/-   ##
=======================================
+ Coverage   80.0%   80.5%   +0.5%     
=======================================
  Files         13      13             
  Lines        698     716     +18     
=======================================
+ Hits         559     577     +18     
  Misses       115     115             
  Partials      24      24             

Impacted Files	Coverage Δ
config.go	88.8% <ø> (ø)
driver.go	94.7% <ø> (ø)
conn.go	78.2% <100.0%> (+0.8%)	⬆️
connector.go	100.0% <100.0%> (ø)
rows.go	54.5% <100.0%> (ø)
sql.go	80.9% <100.0%> (ø)
stmt.go	77.1% <100.0%> (+2.5%)	⬆️
tx.go	100.0% <100.0%> (ø)
utils.go	95.0% <100.0%> (+0.1%)	⬆️

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[XSAM]

@fantapop Thank you for raising this PR and for the quality work! 👍🏽

I am still reviewing test cases, and it could take some time.
Some comments might need to be solved.

[fantapop]

I pushed some fixup commits. I'll squash those into the one commit before merging. I've left some usage of the term omit within the code base since it was already existing and seems to be clearer to me whats going on. Let me know if you want me to change it.

[fantapop]

Hi, have you had a chance to further vet this PR?

[XSAM]

LGTM! Comments might need to be resolved.

[XSAM]

@fantapop Thanks for your contribution! 👍🏽