support extracting placeholder from non-normalized expressions, e.g. ${user.address}/user/gateway

[nobodyiam]

What's the purpose of this PR

support extracting placeholder from non-normalized expressions, e.g. ${user.address}/user/gateway

Which issue(s) this PR fixes:

Fixes #3138 #3169

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[codecov-commenter]

Codecov Report

Merging #3178 into master will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #3178      +/-   ##
============================================
+ Coverage     51.53%   51.55%   +0.01%     
- Complexity     2253     2255       +2     
============================================
  Files           433      433              
  Lines         13447    13447              
  Branches       1378     1378              
============================================
+ Hits           6930     6932       +2     
+ Misses         6037     6036       -1     
+ Partials        480      479       -1     

Impacted Files	Coverage Δ	Complexity Δ
...work/apollo/spring/property/PlaceholderHelper.java	78.46% <0.00%> (-1.54%)	24.00 <5.00> (ø)
.../framework/apollo/spring/property/SpringValue.java	89.47% <0.00%> (+1.75%)	21.00% <0.00%> (+1.00%)
...rk/apollo/spring/property/SpringValueRegistry.java	88.88% <0.00%> (+5.55%)	11.00% <0.00%> (+1.00%)

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