fix(schema-compiler): Free jinja instance after compilation

[ovr]

Jinja instance stores all templates, because it resolves dependencies inside minijinja. If we have at least one jinja file, then compiler load all templates to jinja instance.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.64%. Comparing base (d8b8deb) to head (09e017a).
⚠️ Report is 4 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (d8b8deb) and HEAD (09e017a). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (d8b8deb)	HEAD (09e017a)
cubesql	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #10169       +/-   ##
===========================================
- Coverage   83.28%   54.64%   -28.64%     
===========================================
  Files         244      214       -30     
  Lines       74180    16995    -57185     
  Branches        0     3471     +3471     
===========================================
- Hits        61781     9287    -52494     
+ Misses      12399     7208     -5191     
- Partials        0      500      +500     

Flag	Coverage Δ
cube-backend	54.64% <100.00%> (?)
cubesql	?

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