Optimize SqliteDataReader.GetFieldValue

[roji]

Following a discussion on generic methods, this optimizes SqliteDataReader.GetFieldValue to take advantage of JIT elision when doing value-type checks. The mechanism (with produced assembly code) can be seen here.

Note that we can optimize nullable value types in the same way (int?) if we want. While looking at this I noticed that GetFieldValue returns null if an unknown nullable type is requested and the database returns null; in other words, GetFieldValue<Blog>() doesn't throw, but rather returns null, which is a bit odd.

/cc @AndriySvyryd

[roji]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

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[ghost]

Apologies, while this PR appears ready to be merged, I've been configured to only merge when all checks have explicitly passed. The following integrations have not reported any progress on their checks and are blocking auto-merge:

1. Azure Pipelines

These integrations are possibly never going to report a check, and unblocking auto-merge likely requires a human being to update my configuration to exempt these integrations from requiring a passing check.

Give feedback on this

From the bot dev team

We've tried to tune the bot such that it posts a comment like this only when auto-merge is blocked for exceptional, non-intuitive reasons. When the bot's auto-merge capability is properly configured, auto-merge should operate as you would intuitively expect and you should not see any spurious comments.

Please reach out to us at [email protected] to provide feedback if you believe you're seeing this comment appear spuriously. Please note that we usually are unable to update your bot configuration on your team's behalf, but we're happy to help you identify your bot admin.