Add type aliases and literals up to uint512

[chfast]

Fill the gap in the type aliases and literas in the range 128-512. Also place the literal operators in the intx::literals namespace to allow using the literals without using namespace intx.

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.94%. Comparing base (394c5bc) to head (e6c457f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #317   +/-   ##
=======================================
  Coverage   99.94%   99.94%           
=======================================
  Files          10       10           
  Lines        1892     1892           
=======================================
  Hits         1891     1891           
  Misses          1        1           

Flag	Coverage Δ
32bit	99.94% <ø> (ø)
gcc	99.41% <ø> (ø)

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Files with missing lines	Coverage Δ
include/intx/intx.hpp	99.86% <ø> (ø)
test/unittests/test_intx_api.cpp	100.00% <ø> (ø)