Sepolia network added

[NickSneo]

What does this PR do?

Adds support for Sepolia network

Where should the reviewer start?

all files

Why is it needed?

Sepolia was't supported before
Resolves - #1928

[codecov]

Codecov Report

Merging #1971 (878758f) into master (ac0618c) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #1971      +/-   ##
============================================
- Coverage     68.49%   68.48%   -0.02%     
+ Complexity     3004     3003       -1     
============================================
  Files           488      488              
  Lines         12559    12561       +2     
  Branches       1637     1638       +1     
============================================
  Hits           8602     8602              
- Misses         3482     3483       +1     
- Partials        475      476       +1     

Files	Coverage Δ
core/src/main/java/org/web3j/ens/Contracts.java	76.92% <100.00%> (+4.19%)	⬆️
core/src/main/java/org/web3j/tx/ChainIdLong.java	0.00% <ø> (ø)

... and 1 file with indirect coverage changes

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[cfelde]

LGTM