use correct identity to initiate delete in HDFS

[wliufle]

Description

Currently, ThriftHiveMetaStore uses HdfsContext to get the file system and delete the partitions when hive.metastore.thrift.delete-files-on-drop is turned on. The HdfsContext is initialized using a DEFAULT_METASTORE_USER which is presto. So when Trino initiates delete operations, user authentication uses the presto user for getting HDFS file system. This is fine when impersonation is turned off, since the underlying user can be obtained from the hadoop system in DirectHdfsAuthentication. But in ImpersonatingHdfsAuthentication, it uses the presto user to create proxy user.

Is this change a fix, improvement, new feature, refactoring, or other?
fix

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)
hdfs in hive metastore

How would you describe this change to a non-technical end user or system administrator?
Trino used to use the dummy user in ThriftHiveMetaStore to get HDFS file system and this fails when the real user is needed if it's impersonating another user.

Related issues, pull requests, and links

Documentation

(x ) No documentation is needed.
( ) Sufficient documentation is included in this PR.
( ) Documentation PR is available with #prnumber.
( ) Documentation issue #issuenumber is filed, and can be handled later.

Release notes

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( ) Release notes entries required with the following suggested text:

# Section
* Fix some things. ({issue}`issuenumber`)

[phd3]

Merging, as changes requested by @electrum have been addressed