Added readonly modifier to private fields which are never changed

[Lehonti]

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature (N/A)
• I have successfully run a local build

[martincostello]

Thanks for your contribution.

As you can see, the build is now failing due to readonly being incompatible with other uses of these fields in the code. It may be that all of these fields are already not readonly for that very reason.

Please run the build locally and fix any issues to continue with this contribution.

[Lehonti]

You are absolutely right.

I managed to reproduce the errors in my local environment, and removed the problematic readonly modifiers. As you can see, there are now less files that have been modified when we compare the PR code to the original (used to be 9, now they are 6).

[martincostello]

The changes are now hitting lint errors. Please get a full clean build locally before pushing further changes.

[Lehonti]

No problem. I planned to fix the linting issues in a future PR, but I didn't have any idea that they were configured to make a build fail. It's understandable, of course. You want to keep the code clean.

The built succeeded in my machine without errors or warnings.

[codecov]

Codecov Report

Merging #1451 (8799e05) into main (f8bea05) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1451   +/-   ##
=======================================
  Coverage   83.90%   83.90%           
=======================================
  Files         273      273           
  Lines        6516     6516           
  Branches     1012     1012           
=======================================
  Hits         5467     5467           
  Misses        840      840           
  Partials      209      209           

Flag	Coverage Δ
linux	83.90% <ø> (ø)
macos	83.90% <ø> (ø)
windows	83.90% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/Polly/Caching/AsyncCachePolicy.cs	100.00% <ø> (ø)
src/Polly/Caching/CachePolicy.cs	100.00% <ø> (ø)
src/Polly/Timeout/AsyncTimeoutPolicy.cs	87.87% <ø> (ø)
src/Polly/Timeout/TimeoutPolicy.cs	86.66% <ø> (ø)
src/Polly/Wrap/AsyncPolicyWrap.cs	80.51% <ø> (ø)
src/Polly/Wrap/PolicyWrap.cs	80.28% <ø> (ø)

[martincostello]

Thanks!