feat: disable borrow when nft price is stale

[thorseldon]

• Oracle Keeper set the price stale flag to true when NFT price changing sharply, e.g. up or down exceed 20%;
• Borrowing logic add checks for the NFT price flag is valid or not;

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.

Project coverage is 90.91%. Comparing base (b7b36e1) to head (992989f).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
contracts/protocol/NFTOracle.sol	87.50%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #130      +/-   ##
==========================================
+ Coverage   90.82%   90.91%   +0.08%     
==========================================
  Files          37       37              
  Lines        2868     2895      +27     
  Branches      450      455       +5     
==========================================
+ Hits         2605     2632      +27     
  Misses        263      263              

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