feat(sql): support show sources

[neverchanje]

What's changed and what's your intention?

• SHOW SOURCES [FROM <schema>]
• SHOW MATERIALIZED SOURCES [FROM <schema>]

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #1775 (4c9e181) into main (cba8e3c) will increase coverage by 0.17%.
The diff coverage is 81.08%.

@@            Coverage Diff             @@
##             main    #1775      +/-   ##
==========================================
+ Coverage   71.21%   71.38%   +0.17%     
==========================================
  Files         604      605       +1     
  Lines       78261    78660     +399     
==========================================
+ Hits        55731    56149     +418     
+ Misses      22530    22511      -19     

Flag	Coverage Δ
rust	71.38% <81.08%> (+0.17%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/frontend/src/catalog/root_catalog.rs	77.86% <ø> (+5.89%)	⬆️
src/sqlparser/src/keywords.rs	100.00% <ø> (ø)
src/frontend/src/catalog/schema_catalog.rs	81.94% <73.68%> (+7.36%)	⬆️
src/frontend/src/handler/show.rs	81.94% <76.78%> (+81.94%)	⬆️
src/sqlparser/src/parser.rs	92.54% <77.77%> (+0.01%)	⬆️
src/frontend/src/test_utils.rs	69.87% <87.50%> (+0.95%)	⬆️
src/frontend/src/handler/mod.rs	41.02% <100.00%> (+3.52%)	⬆️
src/sqlparser/src/ast/mod.rs	86.74% <100.00%> (+1.09%)	⬆️
src/source/src/parser/common.rs	73.46% <0.00%> (-6.54%)	⬇️
...ream/src/executor/managed_state/aggregation/mod.rs	78.87% <0.00%> (-5.98%)	⬇️
... and 27 more

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[yezizp2012]

LGTM!