pgwire: Add support for cursors enclosed in quotes

[rimadeodhar]

In CockroachDB and Postgres, it is possible to declare cursors with invalid identifiers enclosed within double quotes, for e.g. "1-2-3". However, when attempting to look up the cursor during pgwire DESCRIBE step, it is necessary to enclose the cursor name within double quotes while looking up the cursor name within the CRDB code. We don't currently do this, which causes the cursor look up to fail during the DESCRIBE step. In this PR, the cursor lookup step has been updated to allow looking up a cursor name created by enclosing it in double quotes.

Resolves https://github.com/cockroachdb/cockroach/issues/84261

Release note (bug fix): The pgwire DESCRIBE step no longer fails with an error while attempting to look up cursors declared by enclosing the cursor name within double quotes.

[cockroach-teamcity]

This change is 

[rimadeodhar]

TFTR!

bors r=knz,rafiss

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error creating merge commit from c0aa573ddccf15ad4b694b91c6198f5d7154d38b to blathers/backport-release-22.1-85859: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

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Backport to branch 22.1.x failed. See errors above.

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