chore: remove compatibility with .meta file

[dkharms]

Description

We no longer support .meta files which were completely substituted with .wal files. This pull request removes all support for .meta file and backwards compatibility mechanisms.

---

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.95652% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.86%. Comparing base (9506076) to head (79fa9a2).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
frac/active.go	86.66%	1 Missing and 1 partial ⚠️
cmd/seq-db/seq-db.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #462      +/-   ##
==========================================
+ Coverage   70.68%   70.86%   +0.17%     
==========================================
  Files         233      232       -1     
  Lines       18399    18293     -106     
==========================================
- Hits        13005    12963      -42     
+ Misses       4416     4351      -65     
- Partials      978      979       +1     

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