fix(proxy-wasm) support get 'plugin_name' in tick context

[thibaultcha]

No filter chain initialized on tick contexts means the root context must be stored in the empty filter chain context for later retrieval.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.82100%. Comparing base (6138510) to head (1e3067c).
Report is 1 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main        #667         +/-   ##
===================================================
- Coverage   90.83814%   90.82100%   -0.01714%     
===================================================
  Files             53          53                 
  Lines          11275       11352         +77     
  Branches        1671        1691         +20     
===================================================
+ Hits           10242       10310         +68     
- Misses          1027        1036          +9     
  Partials           6           6                 

Files with missing lines	Coverage Δ
src/common/proxy_wasm/ngx_proxy_wasm.c	92.70947% <100.00000%> (+0.02387%)	⬆️
src/common/proxy_wasm/ngx_proxy_wasm.h	92.30769% <ø> (ø)
src/common/proxy_wasm/ngx_proxy_wasm_properties.c	89.76035% <100.00000%> (+0.04480%)	⬆️

... and 2 files with indirect coverage changes

Flag	Coverage Δ
unit	90.56263% <100.00000%> (-0.01753%)	⬇️
valgrind	82.47734% <37.50000%> (+0.00853%)	⬆️

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