v1.16: add merkle root meta column to blockstore (backport of #33979)

[steviez]

Problem

Semi-automated backport of #33979; we had previously marked that branch for v1.16 BP in #34046, but I am unable to reopen that PR. This is the same state of those commits with a rebase for tip of v1.16

As for the motivation for this PR (discussion happened in Discord starting from here):

• The new column was backported to v1.17
• Because of the above, a blockstore that has been modified by v1.17 CANNOT be opened by v1.16 due to the extra column
• The above could be problematic for operators who try upgrading to v1.17 and then want to downgrade to v1.16. As we saw in the testnet restart exercise, the "solution" was to wipe rocksdb ... this is unacceptable for mnb
• So, BP this PR to create compatibility between v1.16 and v1.17 branches
• For completeness, backporting Allow Blockstore to open unknown columns #34174 was also considered, but we opted to go with the stub PR as it is logically simpler, and the approach we have used successfully in the past. Once mnb has adopted v1.17, Allow Blockstore to open unknown columns #34174 (which was BP'd to v1.17) should make it such that we'll never have to do any of these "stub column BP's" again

[codecov]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (471956c) 81.8% compared to head (a7b4ee5) 81.8%.

Additional details and impacted files

@@            Coverage Diff            @@
##            v1.16   #34665     +/-   ##
=========================================
- Coverage    81.8%    81.8%   -0.1%     
=========================================
  Files         767      767             
  Lines      209271   209297     +26     
=========================================
+ Hits       171297   171304      +7     
- Misses      37974    37993     +19     

[AshwinSekar]

thanks!

[steviez]

Ok, I manually tested this PR. Namely,

• Ensure node is running fine + caught up with mnb with v1.17
• Downgrade to v1.16.25 and confirm that I see the missing column panic

[...] datapoint: panic program="validator" thread="main" one=1i
message="panicked at 'Failed to open ledger database: RocksDb(Error { message: \"Invalid argument: Column families not opened: merkle_root_meta\" })',
core/src/validator.rs:1608:10" location="core/src/validator.rs:1608:10"
version="1.16.25 (src:8dd7d060; feat:2294205250, client:SolanaLabs)"

• Switch to this PR and confirm that opening the Blockstore succeeds