[WebServer] Mark functions as const + reduce copy of strings

[TD-er]

Description of Change

A few functions in WebServer does have String arguments, which does lead to copying of the strings when calling those functions.
For those where applicable, I changed the function arguments to const String&.

Also some functions which do not modify members, were not marked as const. Added those too.

[github-actions]

Warnings

⚠️

Some issues found for the commit messages in this PR: the commit message "[WebServer] Mark functions as const + reduce copy of strings": summary looks empty type/action looks empty Please fix these commit messages - here are some basic tips: follow Conventional Commits style correct format of commit message should be: <type/action>(<scope/component>): <summary>, for example fix(esp32): Fixed startup timeout issue allowed types are: change,ci,docs,feat,fix,refactor,remove,revert,test sufficiently descriptive message summary should be between 20 to 72 characters and start with upper case letter avoid Jira references in commit messages (unavailable/irrelevant for our customers) TIP: Install pre-commit hooks and run this check when committing (uses the Conventional Precommit Linter).

👋 Hello TD-er, we appreciate your contribution to this project!

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[github-actions]

Test Results

 56 files   -  83   56 suites   - 83   4m 57s ⏱️ - 1h 37m 48s
 21 tests  -   9   21 ✅  -   9  0 💤 ±0  0 ❌ ±0 
135 runs   - 168  135 ✅  - 168  0 💤 ±0  0 ❌ ±0 

Results for commit 161434f. ± Comparison against base commit 4e9eb35.

This pull request removes 9 tests.

performance.coremark.test_coremark ‑ test_coremark
performance.fibonacci.test_fibonacci ‑ test_fibonacci
performance.psramspeed.test_psramspeed ‑ test_psramspeed
performance.ramspeed.test_ramspeed ‑ test_ramspeed
performance.superpi.test_superpi ‑ test_superpi
test_touch_errors
test_touch_interrtupt
test_touch_read
validation.periman.test_periman ‑ test_periman

♻️ This comment has been updated with latest results.

[github-actions]

Memory usage test (comparing PR against master branch)

The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.

Memory	FLASH [bytes]		FLASH [%]		RAM [bytes]		RAM [%]
Target	DEC	INC	DEC	INC	DEC	INC	DEC	INC
ESP32S3	💚 -828	0	💚 -0.08	0.00	0	0	0.00	0.00
ESP32S2	💚 -844	0	💚 -0.09	0.00	0	0	0.00	0.00
ESP32C3	💚 -556	0	💚 -0.05	0.00	0	0	0.00	0.00
ESP32C6	💚 -556	0	💚 -0.05	0.00	0	0	0.00	0.00
ESP32	💚 -832	0	💚 -0.08	0.00	0	0	0.00	0.00

Click to expand the detailed deltas report [usage change in BYTES]

Target	ESP32S3		ESP32S2		ESP32C3		ESP32C6		ESP32
Example	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM
WebServer/examples/AdvancedWebServer	💚 -656	0	💚 -648	0	💚 -368	0	💚 -368	0	💚 -636	0
WebServer/examples/FSBrowser	💚 -688	0	💚 -712	0	💚 -382	0	💚 -382	0	💚 -684	0
WebServer/examples/Filters	💚 -648	0	💚 -640	0	💚 -368	0	💚 -368	0	💚 -648	0
WebServer/examples/HelloServer	💚 -632	0	💚 -648	0	💚 -368	0	💚 -368	0	💚 -652	0
WebServer/examples/HttpAdvancedAuth	💚 -676	0	💚 -712	0	💚 -382	0	💚 -392	0	💚 -672	0
WebServer/examples/HttpAuthCallback	💚 -652	0	💚 -688	0	💚 -402	0	💚 -394	0	💚 -672	0
WebServer/examples/HttpAuthCallbackInline	💚 -660	0	💚 -724	0	💚 -400	0	💚 -392	0	💚 -672	0
WebServer/examples/HttpBasicAuth	💚 -672	0	💚 -712	0	💚 -398	0	💚 -390	0	💚 -672	0
WebServer/examples/HttpBasicAuthSHA1	💚 -672	0	💚 -680	0	💚 -394	0	💚 -386	0	💚 -668	0
WebServer/examples/HttpBasicAuthSHA1orBearerToken	💚 -640	0	💚 -672	0	💚 -398	0	💚 -388	0	💚 -680	0
WebServer/examples/MultiHomedServers	💚 -648	0	💚 -632	0	💚 -368	0	💚 -368	0	💚 -636	0
WebServer/examples/PathArgServer	💚 -660	0	💚 -680	0	💚 -360	0	💚 -360	0	💚 -644	0
WebServer/examples/SDWebServer	💚 -672	0	💚 -724	0	💚 -388	0	💚 -388	0	💚 -684	0
WebServer/examples/SimpleAuthentification	💚 -640	0	💚 -648	0	💚 -368	0	💚 -368	0	💚 -632	0
WebServer/examples/UploadHugeFile	💚 -716	0	💚 -772	0	💚 -456	0	💚 -440	0	💚 -712	0
WebServer/examples/WebServer	💚 -828	0	💚 -844	0	💚 -556	0	💚 -556	0	💚 -832	0
WebServer/examples/WebUpdate	💚 -620	0	💚 -616	0	💚 -308	0	💚 -298	0	💚 -604	0

[TD-er]

Wow, quick merges :)