refactor: move extract_template_files into common crate

[AlexD10S]

Refactor the extract_contract_files function, currently used for generating new contract templates in a monorepo with multiple templates, and move it into the pop_common crate.
This will allow us to reuse the function for parachains with the upcoming integrations.

[codecov]

Codecov Report

Attention: Patch coverage is 62.13592% with 39 lines in your changes missing coverage. Please review.

Project coverage is 70.28%. Comparing base (43e4cd0) to head (3636398).
Report is 2 commits behind head on main.

Files	Patch %	Lines
crates/pop-common/src/templates/extractor.rs	70.31%	0 Missing and 19 partials ⚠️
crates/pop-contracts/src/new.rs	30.00%	6 Missing and 1 partial ⚠️
crates/pop-cli/src/commands/mod.rs	0.00%	4 Missing ⚠️
crates/pop-cli/src/main.rs	0.00%	2 Missing ⚠️
crates/pop-contracts/src/node/mod.rs	50.00%	0 Missing and 2 partials ⚠️
crates/pop-parachains/src/new_pallet.rs	0.00%	0 Missing and 2 partials ⚠️
crates/pop-cli/src/commands/build/spec.rs	0.00%	1 Missing ⚠️
crates/pop-common/src/sourcing/mod.rs	0.00%	1 Missing ⚠️
crates/pop-parachains/src/utils/helpers.rs	0.00%	1 Missing ⚠️

@@            Coverage Diff             @@
##             main     #283      +/-   ##
==========================================
+ Coverage   70.22%   70.28%   +0.06%     
==========================================
  Files          51       52       +1     
  Lines        8673     8657      -16     
  Branches     8673     8657      -16     
==========================================
- Hits         6091     6085       -6     
- Misses       1630     1636       +6     
+ Partials      952      936      -16     

Files	Coverage Δ
crates/pop-cli/src/commands/build/contract.rs	61.11% <ø> (ø)
crates/pop-cli/src/commands/build/mod.rs	50.70% <ø> (ø)
crates/pop-cli/src/commands/build/parachain.rs	73.17% <ø> (ø)
crates/pop-cli/src/commands/call/contract.rs	0.00% <ø> (ø)
crates/pop-cli/src/commands/new/contract.rs	48.05% <100.00%> (ø)
crates/pop-cli/src/commands/new/parachain.rs	45.68% <100.00%> (+0.14%)	⬆️
crates/pop-cli/src/commands/up/contract.rs	25.65% <ø> (ø)
crates/pop-cli/src/commands/up/parachain.rs	7.55% <ø> (ø)
crates/pop-cli/src/common/contracts.rs	0.00% <ø> (ø)
crates/pop-common/src/build.rs	100.00% <100.00%> (ø)
... and 23 more