Use unique_ptr for pcoinscatcher/pcoinsdbview/pcoinsTip/pblocktree

Summary:

• pcoinscatcher (CCoinsViewErrorCatcher)
• pcoinsdbview (CCoinsViewDB)
• pcoinsTip (CCoinsViewCache)
• pblocktree (CBlockTreeDB)
• Remove variables shadowing pcoinsdbview

This is part of Core PR11043

Depends on D1909

Test Plan:

make check

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1910